you could upload your pictures to an image host such as Imgur.com and post the BBCode link in the forums.
It would also be cool if you added a description to your images, although not required.
BBCode example
[img] URL [/img]
OR
[img width=500 height=350]URL[/img]
Here is a video of how to find your screenshots
http://youtu.be/e_ZNiYk_ljo (http://youtu.be/e_ZNiYk_ljo)