If you'd like to edit your signature, click on your name in the top right hand corner of the screen. You'll then be able to select Signature, the second tab on the left.
If you're a Free Member you'll have 3 lines and 240 characters for your signature. You won't be able to include hyperlinks.
If you're a Full Member you'll have 5 lines and 400 characters for your signature. You will be able to include hyperlinks.