Cisco 871W Router

Hoping someone can help. Just purchased, for the school, a Cisco Wireless Router, 871W model. Plugged everything in, connected (via one of the LAN ports on the router) into the network. Disabled DHCP server on it, as the school already has one. Set up an IP address manually. My assumption was, that because LAN and WAN are bridged on the router, if any wireless devices try to connect via the WAN, the DHCP server on the LAN will assign the right IP address, and everything should work fine.
However... trying with a number of wireless devices, none of them are even finding the wireless router. Can anyone advice on what could be the problem, and what settings I should use, and where, on the router? THis is really quite important for me, and the school!

Adam