Whether you are using Macs or PC makes absolutely no difference in how you configure your router.
Macs are really like a foreign language. It is like walking up to your average person and speaking French - they will just repond in English - only louder. What you have to do is speak in their language and translate (silently - to yourself) into Mac-speak. If you tell them you use Macs, they will clam up and refuse to help. That is because all they know how to do is tell you to insert a spyware-laden CD into your computer. Luckily, that CD doesn't work on a Mac. Even better still, you don't even need it.
Ok. Rant over. I've got that out of my system for another 23 minutes...
All you need to do is figure out how to connect the router to the DSL modem. There should be a cable from the DSL modem to your Mac. Unplug it from the Mac and plug it into the Linksys router. There is one Ethernet port different from the other 5, use it. Next, take two more Ethernet cables. For each Mac, plug one end of a cable into the Mac's Ethernet port and the other end into one of the ports on the router. Don't use the port nearest the power plug.
At this point, everything is connected properly. In a perfect world, it would all work. But, as usual, there is more to it. I don't know how ATT DSL connects. If it is using PPPoE, you can (from one of the Macs) go to
the router configuration page, enter your PPPoE id and password, and you should be done. If not, wait for an answer here by another ATT DSL customer or post a question on
the DSL Reports ATT DSL Northeast forums.
I actually though that I would just pop over to the att.net site myself and get the router setup instructions and just post a link here. Boy was I wrong! You are right about ATT. It really reminds me of the ATT of the good 'ole days. To quote their tech support page:
AT&T DSL Service does not support the use of the service through multiple computers.
AT&T DSL Service technical support does not support Networking Routers.
AT&T DSL Service support representatives do not provide technical support for configuration or installation to Macintosh users.
Friendly, huh?
Try the instructions above and see if they work. If ATT is using PPPoE, they must have given you and id and password with instructions where to enter it using some wacky PC software. If not, post whatever instructions you have and we'll try to make sense out of it here.