Do you mean from this website? That would be clicking the picture of you on the top right corner, opening the drop-down menu and selecting "Signature" on the left-hand side. Or do you mean those fancy signatures you see people like SkyDragon and PenguinDJ have? I would have no idea >.>
Mine is just fancy text I threw together at http://cooltext.com. AlexChance makes great signatures, though.