Configuration behind Router Help

[godhand360]

Hello,

This is my first time doing using OPNSense and I need a little bit of help configuring my settings behind my ISP's router Modem/Router (AT&T gigabit).

Anyway I just built a new computer to install this on. I'm not sure the specs really matter but the Motherboard is a Gigabyte H270N Wifi, which has two gigabit ports on board and I installed a Gigabit Intel NIC in the PCI slot so I would have a total of 4 Ethernet Ports for now.

The setup I'm trying to achieve is basically:
                                                                                                                     <----> LAN
                                                                                                                     |
ISP Router (Internet Port) <--> (WAN Port) OPNSense firewall/VPN Client   <----> Ubiquiti AC Lite Wifi AP (OPT 1)
                                                                                                                     |
                                                                                                                     <----> OPT 2 (another LAN)

I've done the initial setup as per this youtube video https://www.youtube.com/watch?v=JD5wtyBAWMA&t=1088s
So the WAN has an DHCP address given to it by the ISP Router. I put the LAN on a different subnet of 192.168.3.1 and enabled DHCP on it as well so I could access the Web Interface.

 I wasn't quite sure how to set it up the AP other than its SSIDs and passwords but it does not have a subnet assigned yet (I'm pretty sure it also has its own DHCP turned on which may be the wrong thing to do so any help on that would be appreciated as well!)

Anyway, after going through that initial configuration and the GUI wizard I still cannot connect to the internet. Is there something that I'm not doing properly or that I need to do in order to do so?