to take a screen shot, there is a button in the top right corner of the keyboard, next to the insert and delete keys, that says print screen (or some shorter version, probably "prtn scrn"). Hit that key, then open up paint or another image editing program, and go Edit/paste. Crop off the extra background and save it (jpg would probably work best).

The you have to find a site to host it. I use tinypic.com alot. You don't have to register to host there. If gives you the code you need, just pop that into your post and there's your pic.

On a side note, if you hold alt (I think) when you press print screen, it will only copy that window instead of the whole screen.