Once the screen shot is taken, if you want to upload it online, for example this forum. Open up paint, and hit CTRL+V or just right click and paste. Then save it as a JPEG. Then you can upload it to many online image hosters. My personal favorite is
www.imageshack.us, because it automatically creates thumbnails so you can post them on forums, instead of posting your huge screen shot. Not only that, but it also creates the code to paste it on the forum, and it also generates the html code as well. The upload size per img is 1 mb.