First, you need to have a picture hosted somewhere that you want as your sig pic. Suppose you do and the URL is
kttp://www.thisistheurl.com/photo1.jpg
(Obviously, a real URL would begin with http, I have used kttp so it will appear as ordinary text.)
Here's what you do to make it part of your signature:
1. Click on "User CP" which is in white letters on the blue bar near the top of the TMF main page. It is the left-most link on that blue bar; the right-most like is "Log Out".
2. Near the left side of the page, near the top, under "Control Panel" and under "Settings & Options" under that, you will find "Edit Signature". Click on "Edit Signature".
3. In the editing window under "Your Signature:", put in this, but with NO SPACE between the IMG and the ]
(I put a space so it would not be treated as an image command.)
[IMG ]kttp://www.thisistheurl.com/photo1.jpg[/IMG]
4. Click on "Save Signature" under the bottom of the editing window.