1. Connect cable modem to cable. Connect power too.
2. Connect Mac's ethernet port to cable modem's ethernet port.
3. Enjoy.
It really is that simple. You don't need any help except for the possible additional chunk of TV cable to wherever you want to put the modem.
Note that T-W has a habit of using VERY small print and very small-print tactics. That $19.99 a month offer will expire exactly on time, and unless you can take advantage of a new promotion, you're, as they say, "hosed."
Also note that you don't always get the best deal on AT&T DSL over the phone.
Look at their web site-I managed to get their
6Mbps package for about the same price as the 1.5Mbps package by committing to a contract (I ain't movin'!) and doing so within my renewal window. Shop and save, as they say!