Just changed my dsl and I have a router too.

you'll need to use your web browser to access and configure the modem, like this:
1) connect your computer ethernet to the running modem, wait about 1 minute..
2) click start, run, type cmd in the run dialog, click ok
3) in the command window type ipconfig then enter. write down the gateway address, probably 192.168.0.1 or something similar
4)open your browser, wait for the error, then type that address into your address bar. that should get you into the modem where you can do it's setup.