Ubiquiti U6+ access point

How do I use a ubiquiti access point alongside the built-in ap of orange? I can connect and use the U6+ ap, but any device that connects to it gets a new ip address (end up with a new device in list for each device that has connected to each ap).

I have one local network set up that has two wifi ssid's (under wifi settings)  on the firewalla ap, and an additional one for the U6+.

I'm not sure if it's just not possible to have the U6+ be part of the orange's ap/wifi or if I'm just getting something configured wrong. 

Any help or advice would be appreciated.