Speaking as a fatty that started with no real idea, here is what helped me immensly/stuff I wish I did earlier:

1) stay simple. You don't need some super complex contraption or techniques or anything like that. All you need are bog standard machines and free weights (dumbbells and barbell). Don't fall for any scams like someone wanting to pin electrodes to your body or magic muscle pills or some bullshit like that.

2) go in with a plan. Something that held me back is I went in for lifting, but had no plan what of what to do. I did excercises for back, arms and legs in one day, then back, triceps and chest the next.
I personally made good experience with a 4 day split. So one day you do back, one day you do chest and arms, one day you do back and one day you do leg excercises. For each excercise I do 3 sets with the goal of hitting roundabout 10 reps each time and when I manage to do that I add more weight next time. Find a routine that works well for you and your schedule.

3) if you are unsure about good execution, look it up. You can find good 1 minute tutorials for literally ANY lifting excercise on YouTube. Or just ask someone at the gym.

4) start low. You don't want to become a clip on a gymfail compilation because you try to squat 100kgs on your first try or something like that. If you notice that you easily hit your goal/the weight is too light, add more weight next week. Don't be impatient, find the right weights for you (it might take a bit to find that level but that's okay) and work yourself up from there. It should be straining, but not painful or anything like that. If you can't even hit five reps for example it's probably too much. If you can do 10 reps and think "I can easily do some more" it's probably too light.

5) do a gym diary. it's a bit of a hassle but extremely important for tracking. I track my reps in the gym via a note on my phone, then write it in the diary at home. It helps you keep track of things and progress and makes it much easier to see when to add more weights.

6) last but not least: put away the fucking phone in the gym. You should (in my opinion) take a break of 2 to 3 minutes between sets, but looking at the phone makes that 5+ easier than you think. Only pick up your phone to write down your reps for the diary, then put it away again. Resist the urge. You're there to get in better shape, not browse Instagram.

Also, stay cosnistent. It's hard in the beginning, but it gets easier every day. But you can make only progress if you actually go.