In case this helps anyone. Here is a step by step guide to setting up the Pi/FPP to work with your wifi. I had a frustrating day trying to enable the wifi on a Pi and I stumbled onto this post Newbie, documenting his efforts. and all my problems were solved. 2nd Pi went off without a hitch. I think the key thing that I was forgetting was the shutdown steps. I don't know Linux but I'm guessing this is required to finalize and setup the changes. Checkout the guys post if you want more details or pictures. He has a PDF you can download.
Here is my condensed list.
1. Format SD card with SD formatter
2. Load FPP files onto SD card (12 files)
3. Erase data on USB flash drive
4. Insert SD card and USB flash drive into Pi and plug in Ethernet cable
5. Plug power cord into Pi
6. After install of FPP, login to FPP via http://IP_ADDRESS
a. I find the IP by logging into my router and looking at connected devices.
7. Upgrade to FPP 1.7
8. Under DNS settings, change hostname to something other than FPP and click save followed by update DNS server. This can also be done later.
9. Shutdown the Pi and unplug power cable
10. Plug WIFI dongle into USB port and leave Ethernet wire connected.
11. Power up Pi. Wait the “standard” 5 seconds before reconnecting the power cord.
12. Login to FPP following step 6
13. Click on the network tab and select wlan. Select static IP and enter desired IP address, or leave as DHCP for now. Enter the WPA SSID and password.
a. Note- most of the wifi dongles only do 2.4 Ghz and not 5 Ghz, so configure router appropriately. Example: My router does both so I have to pick my 2.4 network. I screwed this up the first time.
14. Click update interface and the restart network button once it appears. Click yes
15. Shutdown the Pi and remove power cable
16. Remove Ethernet wire from Pi.
17. Power up the Pi like step 11
18. Login in to FPP using static IP address you assigned, or find it like step 6.
19. Drink a beer, you are now using WIFI to communicate to the Pi.