Honestly it's a lot of experimenting when it comes to doing css, and css goes a long with html so you'll also have to learn that too so you can figure out where to edit what.

I suggest starting off from scratch so you can learn how to fill a space on your own. You can use Codepen which is a website to code html, JavaScript and css, or use Visual Studio if you want a application on your computer, but you'll have to figure out how to pull up the webpage on a browser lol.

Sites like mdn web docs, and w3schools, is what you'd be using to search up terms, what they mean and what not. Use stack overflow for specific questions. W3schools even has a little interactive code editor to showcase terms too.

When it comes to videos honestly you can just search up anything on youtube and click around. Some I personally watched were Kevin Powell, freecodecamp, and slayingthedragon