how do i use RT-AC66U as WAP?

so i have recently got a ubiquiti edgerouter lite. and i plan on using that as my main router.

currently i am just using WAN DHCP, NAT, FIREWALL, and UPNP / Port Forwarding. i am also currently using LAN DHCP on my current isolated test setup (connected to 2 switches and a few computer but not to the main home network yet). the last thing i need to get working on the ERL is QOS.

i would like to use my RT-AC66U as WAP + DHCP, just because the DHCP client is easier to use and no point in moving...

how do i use RT-AC66U as WAP?