Are you saying that you have the Tethering plan and it's not working??

Or, are you asking how to get it working without a tethering plan??

 

PPCGeeks.com AT&T finally catching on to unauthorized tethering – Busted!

EDIT- what you are asking for help doing constitutes a violation of your contract with your carrier and therefor we can not provide help. It's against the Rules of this Forum to assist someone commit fraudulent activity against their carriers. While I personally agree that it's your data, you should be able to use it as you see fit. Helping someone violate their carriers service agreement is no different than helping them defraud the warranty coverage on their phones.

SORRY