If you're trying to post a picture with a comment like this:
Using photobucket.com as an example:
1. Make an account
2. Click "Upload images & videos"
3. Select photo(s) to upload
4. Upload!
5. "Save & Share"
6. Scroll down to where it shows your picture(s) and select the IMG code.
7. Copy and past that ENTIRE code into your comment/post.
Example: http://i222.photobucket.com/albums/dd299/sig.jpg[IMG]
Don't delete any part of the code or you'll get this ugly thing...
[IMG]http://i222.photobucket.com/albums/dd299/RokNRolr/sig.jpg
8. Voila! You're done!
You don't have to use photobucket.com. Most image hosting sites have a similar setup and uploading/sharing process.
Hope this helps!