You don't have to "upload" them to the site, you just display them here. When you upload them to Imageshack, it redirects you automatically to another page, where there are two yellow bars at the top. Right-click on the long web-address in the bar, then click 'Copy'. When you want to put that here on FES, in your new post click on the 'IMG' button above where you type, then right-click and click 'Paste'. Then your picture is in your post.
To simplify:
- Upload image to Imageshack
- Copy web address (the words in the top yellow bar)
- Paste in your post here using the 'IMG' button/tags
If you need any more help, just ask it here.