1. click on print scrn ( on ur keyboard ).
2. open Paint or photoshop or other thing's you can use to edit picture's.
3. edit some things like making it bigger or smaller.
4. go to
www.tinypic.com or other upload site's.
5. click on UPLOAD.
6. it will give you some code's search the [IMG] one.
7. copy it and paste on forums and taadaa you are done.