How did you connect the two routers to each other?

smos wrote

How did you connect the two routers to each other?

Do I have to connect the two routers? I am willing to disconnect my telephone service in order to use the c3150 as it appears to give me depth and range of service I require. Even so, I do not know how to connect the remaining ATT wires to my c3150. Any help and guidance would be appreciated...Thank you.

If you want to use two routers altogether, it's recommended to set up your Archer C3150 as an access point to share your internet.
The connect topology must be as below:
Internet line <-> ATT uVerse router <-> Archer C3150
Please follow the following FAQ link to set up your network:
http://www.tp-link.com/en/faq-1199.html

However, if you want to place the ATT router behind Archer C3150, it's recommended to contact support of ATT for how to set up their router as an access point without using the internet port.