I guess I'll do it.
To have a sig display in your signature section you have to upload said sig to a server host. There are many ones that are free. I use and suggest photobucket.com
You'll have to create an account for it, but its free. Also, I'd be careful about posting adult pictures if I were you, as they do sweeps and will warn you and remove them, and if it happens again they may delete your account. They may also delete your account without warning if you violate any of their other rules. But basically it should be no problem.
This file uploading is not just for sigs, but any other image file for which you plan to display it somewhere. Its pretty simple and straight forward.
Once you upload the picture, you copy the link under "IMG" and paste that in your sig here on TMF. Then it will show up.
Do note that these free servers (or free non-paying accounts rather) do have limited bandwidth. So the larger the sig is, or the more pictures you are displaying anywhere, whether that be at one site or many, the faster your bandwidth will be consumed and the sooner your pictures will fail to show up and you'll get the red x where the picture is supposed to be.
You can create multiple accounts to work around this, but its usually best to keep sigs simple and small enough, not to mention easy on the eyes.