You connect to it with a web browser using the default address. Usually it is »192.168.0.1
or 192.168.1.1 depending on the model. If the modem is in router mode, you can look at the LAN information and see what it is. If the modem is in bridge mode (using a separate router), then this won't work.
Also, if you get a new modem, you will need to call CL Support and get your PPPoE username and password (which are different from your Email username and password) to enter in the modem.