Hello @questkid87!
I do apologize that you are getting sent back to the overview page when trying to add a tablet! I will be happy to help!
Are you bringing over a tablet that was purchased from a third party or directly from AT&T? Check out our support article for bringing your own phone or tablet to AT&T for specific instructions on how to add this to your plan.
If you purchased it directly from AT&T, you usually select the plan when placing the order. In this case, you will just want to activate it! Take a look here for how to activate this new device.
You can also go to an AT&T store to obtain a new SIM card and have the device added and activated for you.
Let us know if you have any other questions or concerns! Have a fantastic day!
Michelle, AT&T Community Specialist