Hi, if you want to connect 2 ADSL routers together via Wireless, one of the two MUST have a Wireless Extender function. If not, it ain't gonna happen!
If you want to connect via cable, then just turn off the DHCP function (important!!) on the second router and connect a cable from any port on one to any port on the other. You should use same SSID and password on both routers also.