It ain't not workin' ~
If you're not sure how to post your image, here's a simple walkthrough:
1. Upload the picture somewhere.
Then you either:
2a. Copy the whole "forum link" thingie they give you. Or "share with friends".
3a. Paste the code in your message.
2b. Get to a point where you see your picture in the largest size available. Then you right-click it and select "copy image link" (or something like that - my Firefox is in French).
3b. Type:
[img]
Paste your code (Ctrl+V)
Type:
[/img]
The final result should be something like this.
[img]http://imagelinkingsite.com/images/yourpicture.jpg[/img]
Or a link to a page where your picture is. Both work. There might be a link around the image code. Don't touch it. It's probably a link to the large version of the picture, while only a thumbnail will display here. That's all right too. In that case, it will look like this:
[url=http://imagelinkingsite.com/displayimage.php?imgid=4987987798][img]http://imagelinkingsite.com/thumb/yourpicture.jpg[/img][/url]