Okay, without getting into any of the reasons why it's easier here than other places or what exactly the computer sees versus having to parse out images with HTML tags etc...
It does help to know if you are working off of a PC or a Mac.
I am assuming (and writing directions for) PC.
I am also going to coach you how to deposit these siggies into your profile, so they will show up with each message.
Posting images:
1. Right Click on the image (in this case, the Tina siggie above).
2. Select "Copy image address".
3. Paste the image address into your message. (a complete address includes the http-through to the dot-jpg or dot-gif)
4. Preview. (My favorite button.)
5. Voila
Now to get it to show up in your profile...
1. Right Click on the image (in this case, the Tina siggie above).
2. "Copy image address".
3. Go back to the "Lobby"
4. Click on "User"
5. Select "Modify your profile and set forum options"
6. At the bottom of your User Profile is the "Signature" section.
7. Paste the image address into this box. (Usually with some sort of reminder of what the siggie is. In this case "BTS/Tina:" http//blahblahblah.gif)
8. Submit changes.
9. Now every time you post a message (or reply to a message) this image address will show up. It will be up to you whether to use it or not for each message but this will be much easier than searching through the messages to find the image again and copy/paste the image address.
Hopefully that was enough help. If not, guide me through your steps and I can reassess the situation.
*crosses fingers*