Well there are bits of info in the FAQs, and Art forums, but what I'd recommend would be to sign up here -
https://buffy-boards.com/forumdisplay.php?s=&daysprune=&f=281 - at the Bad Eggs forum. Hopefully some Artist with a good soul will adopt you, and explain at least some of the "ins and outs". It ain't easy to do the good stuff.
Oh hey, would you like some free info from someone who's been recently playing around to see what's involved though.
The good artists seem to have Photoshop. That's expensive though, and complicated, so what I did was every time I wanted to do a particular function I just checked the freebie download sites to see if there was a program specifically designed to perform that function. Here's a list of a few freebies.
Gimp: It's free and is supposed to be as close to photoshop as you can get without paying anything. It's still complicated though.
Paint.net: A little less complicated, and will still perform a reasonable variety of functions.
Fast Image Viewer: Less complicated, few functions, but it's a good way to organize your pics, and can do a few things.
Fast stone capture: One function but cool. Find a pic anywhere, online, or other, and cut the bit out you want, or save the whole screen.
Edit
You know what I'll do for you? I'll send this thread to the Art forum. You might get some help there. Also once you're there, click to the main forum. You'll see some staked tutorials.