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
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.
If you want to post it as an attached image here is how:
When you post a reply scroll down to 'Additional Options' box and look for the 'Manage Attachments'. Click on this button and a new window will open. In the new window click on 'Choose Picture' and find the picture you want to upload on your hard drive. Once you've added it click on the 'Upload' button on the lower right and then close the window. When you submit your reply it should show up in your post