You now need to Host the image on a site, to be able to post it in the forums. To do that you will first need to go to this site:
http://www.imageshack.us
This is my favourite image hosting site, as it hosts quite big sized pictures at high quality. What you need to do now is click "Browse" and find you saved image. After that you need to make sure the "Resize image" Is not checked and "Remove Size Resolution bar" Is.
after browsing click
START UPLOADWait a moment, because it may take a couple of seconds to uplaod the image. When it has uploaded you will be taken to this Page:
now scroll down n copy the HotLink that is at the bottom of the page, You can either right click and copy or you can press CTRL+C. Now that you have it copied, all you have to do is paste it into your post in the forums and it's there!