this could of easily gone under the tech center.,
anyway, let me see if i can shed some light on it.
Join up by simple registration.
once registered, when log in you'll see an "Image" then a blank box where you can browse your computer to upload a picture file from your computer onto the internet
then hit "upload"
After uploading, upon success, it will show you a thumbnail(small pic) of ur pic u uploaded, and below it are a bunch of (or 3 codes so you can view it on websites,forums, etc.)
for signatures most forums use bbc which is the "img" box, just copy whats in there and paste it to your signature profile.
simple code, [img] <<is what helps it view, and the url that goes in it , is where you pic is located on the net so it shows up.
^is should look something like that, but with an actual url
[IMG ]http://www.blahblah whatever the url of your desired pic is[/IMG]