go to http://www.imageshack.us. Click on browse and upload your signature from your pictures or wherever it is stored on your computer. Imageshack will then give you several links to choose from.
Copy and paste the ‘direct link’ which is the end one I think, but check to make sure. Copy and paste the direct link by click on your left mouse button and dragging it along the link, the right click and select ‘copy’
Come back to your profile on Just Chat, scroll down untill you see a large area for signature. Right click on this area and select ‘paste’. This will add the link for your signature.
Dont forget to put at the end, or else it wont work.
For example,