First let's get the sig working. Open the Admin. Panel then go to the users and groups tab, look at the top window on the left side that is labled users, the second one down is the users options button click it. Scroll down to the second big window in the middle of the screen for user settings and you will see the first thing listed is "allow signatures" just make your selection. If that don't do it then see my post about signatures under the please read section. Also when you do this you won't see your sig in prvious posts, only in ones that you make from that point on.
Now to change the Admin name go to the Admin. Panel, click the users and groups tab, go to the ranks box on the left (3rd down), click "rank administration", You should see the "Ranks" box in the middle of the screen, one of the rank titles should be "Admin" just click on the orange gear looking icon to the right side and you can change the rank name there.