First check to make sure that the drive has been formatted in Mac OS Extended (Journaled)
Next, open AirPort Utility on your Mac
Click on the picture of the AirPort Extreme
Click Edit in the smaller window that appears
Click the Disks tab at the top of the next window
Make sure that the name of the drive appears
In the example below, you can see that I have connected a drive named "500 GB Drive". The name of your drive will appear on your screen if the drive is formatted correctly and AirPort Extreme recognizes the drive

Note.....the USB port on the AirPort Extreme is underpowered. If the drive is not recognized, you may likely need to use a powered USB hub with your hard drive, even if the hard drive has its own power supply.
Access the drive on your Mac like you would any other network drive by clicking on the AirPort Extreme under the Shared heading in any Finder window
Finally, what you are trying to do is not officially supported by Apple. They expect you to use the wireless on the AirPort Extreme to access the hard drive, or connect your Mac directly to the AirPort Extreme using Ethernet.
So, your setup may or may not work with a Fios wireless network. It all depends on whether Fios supports the communication protocols that Apple uses on their products.
If you continue to have problems, things would be tons easier.....and have a much better chance of working.....if you could simply connect the USB drive directly to your Mac.