Hello
It is not possible to configure DHCP relay on the AP.
The AP will forward the wireless traffic to a wired VLAN on the switch side. It can be either the default VLAN of the AP (if you dont speficy egress VLAN in the VSC) or some separate non-default VLAN (specified in the VSC menu under egress VLAN).
DHCP relay or ip helper should be configured on the switch or router which acts as default gateway for the wifi client VLAN.
When the CIsco router was DHCP server it was probably working because the router was default gateway and DHCP server at the same time.