here are a few easy steps that should get you posting screenshots!
1. press "prt scr," which is usually next to F12, to take a screenshot of whatever it is you want in your post.
2. open Paint. (Start -> All Programs -> Accessories -> Paint)
3. paste (ctrl+v OR Edit -> Paste
4. crop (cut out) or resize (change the size) if you need to.
5. save (File -> Save as...)
6. go to an image hosting site (like https://www.photobucket.com/)
7. click "Choose File," find the picture (step 5), click "Upload"
8. copy the IMG Code (highlight IMG Code, right click -> Copy)
9. paste (ctrl+v OR right click -> Paste) onto post.
IF YOU HAVE A MAC:
1. take a screenshot (command+shift+3) (command is the apple key, next to the space bar)
2. open the file, which is now on your desktop (usually named Picture 1)
3. crop (cut out) or resize (change the size) as needed
4. export as a JPEG (File -> Export, select Format: JPEG, save as...)
5. follow steps 6 through 9 above.