catcarl, here's a quick little instruction on how to make screenshots:
"Alt" then "PrtSc" (print screen). Next, do "Ctrl" then "V" unless you are on a Mac, then do "Apple" then "V" in a drawing document (this is basically "paste", so if you want to you can go up into "Edit" then "Paste" and it will do the same thing), I use Paint, then once the screenshot is in there, crop any part of it if you need to, then save it. If you know how to post images in BTT you should know how to do the rest.
