The manual for the CenturyLink Westell 7500 Modem contains information about the contents of the modem kit and the installation method. A PDF version of the manual is available on the website of CenturyLink. Use Microsoft Edge on Windows or Preview on Mac OS X to open the PDF manual.
The manual states that a full kit should include the modem itself, a black power cord, a green cord, a yellow Ethernet cable and two phone filters. The manual states that the phone filter is necessary to remove static from the phone line and avoid Internet connection problems. You should use a filter for each phone outlet in your home that has a device plugged in. Ask for additional phone filters by calling CenturyLink at 1-800-244-1111.
According to the manual, you must plug the filter directly to the phone outlet, and then plug the phone cord into the filter. The next step is to plug the power cord into an outlet and into the modem. The green light on the modem should turn solid green after blinking for a minute.
With the two ends of the green cord plugged into the phone outlet and the DSL port on the modem, wait until the DSL light to turns solid green. Then plug the yellow Ethernet cable to the Ethernet ports on the modem and your computer. Once the modem establishes a connection, opening an Internet browser brings up the CenturyLink setup page. Follow the instructions on the Web page, and test to see if your connection works. You can call 1-888-777-9569 to receive help with the online setup.