Setup BASEBOX 2 behind RB2011UiAS-IN

Hello
I have a RB2011UiAS-IN at home configured as my main router. I decided to replace one wireless access point with a BASEBOX 2, but I’m not quite sure how I can set it up as a simple AP behind my main router only serving the wireless clients. The main router should provide DHCP/Firewall and port forwarding to the clients connected to BASEBOX 2.

Thanks.