Problem using 3rd party equipment

I would like to use my own modem. I purchased a Motorola MB7420, which is on the list of Xfinity compatible modems.

I tried to activate it last week with the help of an Xfinity support person, but did not succeed. The problem was that even though the modem connected to Xfinity via the cable, there was no Wi-Fi network. The Xfinity support person said I had to set this up myself, but I reviewed the documentation and it said that Xfinity has to "provision" the modem. There is no way for me to do this. Can someone who understands this issue help me connect my equipment?