Plug the second router in to the first router's Uplink port. If it doesn't have one, plug it in to port 1 and look for an uplink button or switch. Also, disable DHCP on the second router and set its ip to 1 more than the 1st router. (Example: Router 1: 192.168.0.1, Router 2: 192.168.0.2)
You might have to mess with configurations and such, but try that.