Hey Tokijin. Name's DB, and welcome to our little family, enjoy your stay. Trust me, you'll make plenty of friends, so long as you stay out of trouble.
Now, in response to your question, you get sigs by going into your profile settings (See the top of the page; Signed in as (Insert name here)), click your name, then click the Signature tab. In the text box, you paste the IMG code of your chosen image. Check the rules as to the size constraints. To find the IMg code, you should upload the image onto a site such as Photobucket, they display the IMG code for every image in your album. If you ever want a sig made for you, request one in the Sig-Avatar Requests thread, and the graphics crew will try their best to make you one. And trust me, they're good. Damn good.
Note: Yes, I'm the first to reply =)

Are you ready for the changes?