If your Hotspot is configured on ether2, and ether3 is available, set the master-port of ether3 to ether2. The two are now bridged via the built in chipset at wire speed. Now plug a LAN port of the AP into ether3, give the AP an IP on the Hotspot network (yuck), and turn off the DHCP server on the AP. That's it.
Specific answers require specific questions. When in doubt, post the output of "/ip address print detail", "/ip route print detail", "/interface print detail", "/ip firewall export", and an accurate network diagram.