AT&T go phone in AT&T iPhone 5?

I have a AT&T iPhone 5 and had it shut off cause it was exspencive. Befor I had AT&T gophone and used it in a iPhone 4S I was wondering do I have to buy a AT&T go phone to activate then put it in my iPhone 5 or can I go online and just buy a gophone SIM card and activate it into my iPhone?

You don't have to buy an AT&T go phone to activate. The sim is what identifies the phone to the network.

Personally I would go to an AT&T corporate store and buy the sim and have them set the phone up for you. That way you can have any questions or technical issues dealt with on the spot.

You are in the wrong forum. This is for landline phones, not smart/cell phones