Mel ,
You would need to get a router and a second cable for the second computer.
you would connect the DSL modem to the router and then plug in the 2 computers to the router.

The router is what separates out the "communication" from each computer and sends it where it needs to go.

If you just plugged into a phone line the communications would just get all jumbled together. Probably like a busy line signal.

Or you could go wireless too, but then would need wireless router and wireless cards inside the computers.

but if you have the room for the computers to be close to each other and to the dsl modem, a "wired" cable conncetion is easier.
Usually just plug it in and use it.

here's a site with tips and pictures about routers and set up
http://www.onlinecomputertips.com/ne...ng/router.html