By made the connection, I assume that you mean your attached an Ethernet cable from the uverse LAN port to the Wireless N router LAN port?
Did you turn off the wireless radio in the uverse? You have to decide how to configure it, but I would turn off DHCP service in the Wireless N -- let the uverse continue to do that (and continue to use the uverse as the gateway address for the internal network), turn off the uverse wireless radio, give the Wireless N an address on the network that is outside the assignable DHCP range on the uverse.
So for example if the uverse gateway address is 192.168.1.1, make the wireless N 192.168.1.2 and let the uverse DHCP assign 192.168.1.3 to .254
Configure the wireless N security, say WPA2 and enter a passphrase, which will also be entered in all your connecting devices.
The result of doing the above is continuing to use the uverse as your gateway router (without wireless G) and configuring your Wireless N as an access point to provide the wireless service for your network.