Send 100,000 TC to any administrator (Creati0n, Fear, Icky, Rai, Reta) with the name you want. Every time you get a name change the price doubles, so if you were to get a second name change it would cost 200,000, then your third 400,000 and so on. You could also pay a flat rate of $25.

You can get more information here
http://forum.toribash.com/showthread.php?t=343024
http://forum.toribash.com/showthread.php?t=572696