OK, just went through this again and I blogged it, but here are some of the quick notes:

1. When you get the Edge Router, the first thing you should do is to upgrade the firmware. The EdgeRouter POE installation didn't have any Wizards, so you need to go to the System menu at the bottom then you click on the link to Download. The EdgeRouter has lots of similar names, but the EdgeRouter X is not the same as the Edgerouter POE. And if you select incorrectly, the firmware will refuse to load.
2. When you reboot the Edgerouter, you won't see the web interface come up for maybe a minute, so be patient. Remember you manually set your computer to 192.168.1.11 and then browse to 192.168.1.1 and make sure you are on Eth0. And also make sure after you configure to move to Eth2-4 as Eth0 is the WAN port and it won't seem to work.
3. The EdgeRouter POE needs to be set to supply POE to the different ports. Make sure you read what your AP accepts so you don't burn it out. For instance the Unifi AP AC Lite needs 24V, but the Unify AP AC Pro needs 48V.
4. When you setup the EdgeRouter make sure to use Chrome. The above setting causes an error on Safari.
5. Once you have this up and going, go to the Wizard, we had the most success with the 2WAN case, so if you ever want to setup a failover, you can do it by putting it on eth1
6. When you connect it all back together, at least on Comcast, it takes a while for the cable modem to give it DHCP so be patient.

For the Unifi AP, you need to:

1. Install the Unifi access software your machine.
2. Then you start a browser
3. You will see the network configuration at the lower left in the gear icon and that is where you setup the network.
4. Then you browse to the dashboard and find the AP.
5. There are lots of settings like Bandsteering that you can play with but the defaults work pretty well.

Finally if you are hooking this up together, you can do something pretty cool:

1. The EdgeRouter X is a passthrough POE device, so you can setup the AC Adapter of your Unifi AC Lite and connect the POE end to the Edge Router along with the WAN connection. This will power the Edgerouter
2. Then you can set eth4 to be a POE passthrough and stick your Unifi AP AC Lite on it and it will get power through it saving you an entire wall wart. Pretty cool huh?

This is meant for remote installations where you want some LAN connections and you want wifi, perfect for the remote location in your home or office.