Hey chris its pretty easy.
create a new document in photoshop with a transparent background. Use the type tool, or brush, shapes whatever you want for your signature.. you can look up online what the copywrite symbol is... ie hold down alt+ three numbers
WHen you get the signature you want to use, crop out the extra.
EDIT>Define Brush... give it a name...bam your done
to use it go to the brush tool, and scroll down the list of your brush choices, and it should be at the bottom... STAMP it!