Here I'm asking does this setup work with other computers or is it a new installation?
If it's new you have to setup the Modem First with a Direct Connection through a wire tot eh Modem. When that is working you then connect the WiFi Access Point and set it up again with a Wired connection. You also set the security on the WiFi Access Point at the same time.
After that is finished and working you then attempt to add the WiFi Connection to the WiFi Access Point by setting up the WiFi Link on the computer that you want to use Tirelessly.
While it is possible to setup a connection like this Wirelessly it's Horrendously Complicated and time consuming. It's really much easier to just use a CAT5 Cable and setup the Internet Connection First then add in the WiFi Access Point.
Col