You can connect the AP' s to any port on the 80CM. <br>
Go the GUI-> System->Network-> Interface and choose the port and select the option " Dedicate this interface to FortiAP Connection"
and it will prompt you to choose the IP address range for DHCP.
For FAP221B, you need to create a custom profile and add the existing SSID (used in the internal WLAN) in the profile and assign the profile to the AP.