Signatures

I have been wanting to add a signature to the end of my posts - you know, like a closing in a little box - to sorta complete my new look. Does anybody know how to do it? I have the picture of my sig. I want to add but I don't know how to do it and I'm afraid to do it wrong and mess up all the hard work that Nan did for me! :)

Any suggestions? I know it can't be too hard, I see them all over the place! :)