Do you want to use your Linksys wireless access point & router to bridge another wired network to wireless?
There isn’t a mode for it in the Linksys setup. There are firmware hacks, but those are another thing completely.
My simple suggestion: instead of using the WAN port for the router’s uplink, just plug the uplink into one of the switch ports on the Linksys. Ta-dum! Instant bridging.