to take a screenshot follow these simple instructions:
1) press the "print screen" button. it will usually be located in the upper right of your keyboard:
this puts a copy of your screen onto your clipboard.
2) open whatever program you use for photos (photoshop, paint, etc).
4) open a new document and press "ctrl+v" to paste.
5)Voilą! you have a screenshot. save, uplaod and post.