There are two ways to add an image to your post. Using HTML code will not work.
The first way to add an image to a post is to simply "attach" it. You can do this by clicking the "browse" button at the bottom of the posting area, then selecting the image file that you want to attach to your post. Once you do that, click the "add this attachment" button. This method only works for posts and not for your signature
The second way is to use bbcode tags. In order for this to work, the image you want to appear in your post has to already be hosted somewhere else on the internet. All you have to do is use the [img] and [/img] bbcode tags. This method works for your posts and your signature as well. Here is an example:
If you would like the image in your post or signature to link to something when people click on it, you have to combine [img] tags and [url] tags. Here is an example:
Just copy it then paste it into your post or signature, and replace the urls with your own.