Click on "Profile" after you log in.
Click "Forum Account Related Settings"
There will be an option to upload your own picture from your computer, or to link one.
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To put an image in a post, copy the image link, [either upload your picture to tinypic or another picture publishing site, or grab one off the internet] and put it in this format:
[IMG.]http://link here[/img]
Remove the '.' after the G, though
http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=53003.0 (http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=53003.0)
Here's a helpful link in case I didn't explain well.