Disregard the children that already have answered this question. They're ... grey-matter challenged.
It sounds like you'll need a wireless router that has Ethernet ports in addition to providing WiFi.
Luckily, that is pretty easy to come by.
You'll buy a wireless router that includes 4 (or more) Ethernet ports. Follow the directions in the user manual that probably will come on the CD that comes with the router and set up PPPoE on the router and Wireless security. I suggest setting up WPA2 security, since WEP and WPA can be cracked in as little as 60 seconds.
Once you've installed the router per the directions, you'll be able to use all of your wireless equipment and continue to connect your main computer view Ethernet connection.
Source(s):http://www.google.com/products?q=consum ... &scoring=p