Basically, my question is what the title is. How do I post screenshots? Any answers will be appreciated.

Upload it to a site such as www.tinypic.com or www.imageshack.us

Then put it between img tags

Ok, thanks.

There's also a little button that looks like a stamp, with two mountains and a yellow background.

you can press that and put the link in there, no need to deal with any code.