If you are using two routers, but want only one to act as the router while the other acts as a WAP (only) but is not a dedicated WAP (if you already happen to have two wireless routers - otherwise, buy a WAP if you are buying) the one acting as a router would be set up normally - you might or might not want to veer away from defaults a bit (ie, there are many, many private NAT networks -- not all of them need to be 192.168.1.0 - there's plenty of options other than that particular one, but it's a common default.)
The router that you want to use only as a WAP should NOT have anything plugged into the WAN port, and should NOT have DHCP enabled. Plug between the/a LAN port and the Switch. It needs a unique LAN IP address in the correct range, and whatever wireless settings you'll set. Some can actually be told that you are using them as a WAP, the rest work just fine if nothing is plugged into the WAN, they have an address of their own, and DHCP is turned off.
So, for a concrete example with numbers (which are not cast in stone, but will work): pick 192.168.42.0/24 as your network, and think fondly of Douglas Adams. Set the LAN address of the router to 192.168.42.1, the netmask to 255.255.255.0, the DCHP range to 192.168.42.101 through 192.168.42.151 (or higher if you need more, but that seems unlikley), your wireless encryption to WPA2, and a long messy password for the wireless. Also set a new password for the router.
Set the WAP to no DHCP, LAN address 192.168.42.10, gateway 192.168.42.1, netmask to 255.255.255.0, your wireless encryption to WPA2, and a long messy password for the wireless. Also set a new password for the (WAP)router; and plug it into the switch.