Ok, we have a xbox 360 elite in a downstairs bedroom. In that bedroom we have a single phone jack. I was told I need a wireless modem to be able to hook the xbox up for a live connection. The actually computer with the modem is upstairs. How will it work if I get a wireless modem? I don't know how it will all work.

Not a wireless modem, you need a wireless router and a wireless network adapter for the XBox. This is assuming you don't want to run a cable from the router and that you have a broadband connection.

OK... I'm an idiot when it comes to this.. tell me how this works. The comper with modem is upstairs. Where do I put the wireless router and adaptor? Does there need to be something at the modem and at the xbox? I have a dsl connection

To share the DSL connection you need to connect the modem to a router. That router performs the function of sharing the Internet from the modem to all network devices connected to the router. Those devices can be connected via an Ethernet cable or wirelessly assuming the router has that capability. Each device needs an Ethernt Adapter (for wired connections) or a wireless ethernet adapter for WiFi connections.

I think XBox has built in WiFi but I'm not sure.

Thanks!

The xbox does not have wifi built in. you will need to buy a wireless adpater or a very long ethernet cable :)