and please make sure to enable WEP so no one hacks or uses your network without permission. That can be set while configuring your wireless router.
Most likely you will have to have your first computer full working with internet through the cable modem. Then you will be told to unhook it and hook up the router. First by plugging in the AC power cord, then pluging the ethernet cable from the cable modem into the WAN
(wide area network) port or the Internet
port on the back of the router as seen in the picture below:
THen you must plug a ethernet cable either into ports 1,2,3,4, or 5 and plug the other end into the computer. Then you computer should have a little icon on the toolbar that says now connected at 100MBPs, icon should look like this, but the screens flashing blue
Then you must configure your router and then you are finished.
Take your second computer and install the wireless adapter card, search for your network, connect to it and type in the WEP code if you have enabled
this and you are finished and ready to surf the net and share files over your wireless network
Hope this helps