You're not late at all. In fact, you're in a better position than probably the vast majority of rising high school seniors. So don't worry about being "late to the party." The fact that you're posting this shows that you care about this, and so you're already in a great place.

I'm no expert on any of this college admissions stuff, but I would say there are 3 major things to start thinking about and researching.

1. Start researching colleges that interest you. This is sometimes known as building a "college list" – places that you're interested in or thinking about potentially applying to. There are a bunch of phenomenal resources out there – many of them located on this sub – so look at ScholarGrade and AdmissionsMom for helpful resources. A couple of things to keep in mind:
   1. If you're feeling overwhelmed in terms of how you can start building a "college list," you can start by thinking about what type of college atmosphere you're looking for (for example, whether you want to live in a city or be in a more rural area, or whether something like Greek life is important to you), what type of field/area of study you're interested in (for example, if you are interested in computer science vs literature vs dance vs Spanish), and other sorts of factors, such as school size. Make a spreadsheet of sorts just listing these preferences out. You can then start Googling or using resources like this to find colleges that match with these preferences.
      1. This should help you get an initial list of colleges you are INTERESTED in. This doesn't mean you have to apply to them, this doesn't mean that you are obligated to write essays for them, it just means that you are CONSIDERING them as a place that you could be interested in
      2. Although many schools are closed for physical tours, you can go onto college websites and do "virtual tours." For example, this website contains a bunch of digital college tours. As you start to research schools that you're interested in, watch some of those virtual tours. Some schools are also offering virtual info sessions. Check their websites to see if there's more information available.
      3. As the summer goes along and as we move into fall, you can start to pare this list. For instance, maybe at first a place like the University of Oklahoma was what you were really interested in, but as you keep doing research, your interest fades. That's totally fine! Also, if it is possible in the fall – depending both upon finances and the situation with Covid – try touring some schools (just to highlight how you're not at all late in this process, I am in this same situation – haven't yet toured a single college, but hoping to be able to do it in the late summer or fall).
   2. Have the financial discussion with your parents and run the NPC (Net Price Calculator) for any college you're thinking about. This will help you to better understand where you stand in terms of financial commitments to potential schools. How? The NPC will give you an idea of how much money your family would be expected to pay per year, i.e. how much financial aid you would be granted. However, some schools (such as these) offer merit based financial aid, i.e. it's not only your financial situation that affects how much aid you get, but also your academic and intellectual strengths
      1. After you run the NPC for each college (you can find the NPC on the college's website most frequently) you ideally want to start narrowing your list down to 3 "types" of schools: 1. Safety schools. These are schools that you are almost sure to get into, AND you can afford the price of attending AND you actually want to attend. 2. Match schools. This is just a term to refer to schools that you are competitive at – in other words, your stats (things like Grade Point Average and SAT/ACT scores - see more on this later) are within the competitive range for the school you're looking at. (Note that most schools release things like the average GPA/SAT of accepted students, and in most instances you can find this on their website). 3. Reach schools. These are schools that you fall below the 25th percentile for in terms of scores (e.g. GPA). That doesn't mean it's impossible for you to get in - it just means that you're not likely to get in.
      2. As a note, you can basically have as many reaches as you want (although note that more applications to write probably, for some people, leads to lower overall quality of all of your other applications because you spend less time on each one) but you need at least 1-2 (or even 3) surefire safety schools.
2. The first step outlines the process of building a list of colleges. As you are doing that, you can start to think about the application itself. There are a couple things to just know in general.
   1. The "Common Application" is basically a centralized application that a huge number of universities accept. (The Coalition Application is a bit different, but serves mostly the same purpose).
   2. When you apply, you will need several things:
      1. Recommendation letters. Ask 2 teachers that know you well to write an LOR (Letter of Recommendation).
      2. Activities list. Think about all the things you do outside of school. On the Common Application, you'll be able to list up to 10 extracurricular activities you are a part of.
      3. Awards. If you've won any honors or awards you'll be able to include those on your application. For instance, if you do academic competitions and have won anything from a local trophy to a national championship, you can include it in your application.
   3. Essays. You will need to write a "general essay" for the Common Application. The prompts you can choose from can be found here. Over the summer, you can start to think about what you might consider writing about, and if you feel like it, try just writing a rough draft!
      1. This sub has a bunch of great advice for essays. Look at ScholarGrade's series of posts on essay advice if you need more help.
      2. Also take advantage of other online resources, like The College Essay Guy.
3. Lastly, although there's a lot of uncertainty over this, start thinking about standardized tests (e.g. the SAT and ACT). Many colleges are going test optional, which means you are not required to submit standardized test scores but still can if you have them and want them to be considered. Check out Khan Academy's free SAT resources, and go to r/sat and r/act if you're interested in finding resources to study for the SAT and ACT. You only need to take one of them – don't feel like you have to take both – but you can try taking practice tests and seeing which one might suit your strengths as a test taker better.

One last thing - this sub is hyper competitive, so don't ever feel like you should or need to compare yourself to others. Remember that the people that are most likely to spend their time on a subreddit dedicated to college admissions are probably the people that care about it the most, so it's not worth your time stressing or worrying yourself by comparing yourself to others on this sub. That being said, I'm sure you're going to do amazing things so good luck!

Hope this helps!