If you want to upload screen captures, or partial screens/windows, the absolutely easiest way is with a utility like this one - but I'm sure they are others. I like greenshot though and use it all of the time.

You just hit the prtsc button and then use the mouse to outline the area of the screen you want to capture. It automatically uploads it to the imgur site by default but you can pick another one if you want. Plus it copies the address to your clipboard so all you have to do is paste it. Works like a charm. I use it even when I could just rt-click an image on a website and copy the location.

For this forum, you can go into preview after typing a few characters in the text box at the bottom of the screen. From there, select the "image" option from the menu and just paste your link in the box.

Btw, the uploads to imgur are anonymous but if you rt-click on the system tray icon and the imgur link one of the options will be to view your history of uploads and even delete items you want to get rid of.