I have downloaded a series of camera views and will install them in camera.cfg in the fnx-aircraft-320\SimObjects\Airplanes\FNX320 folder
Dumb Question: How do I access these camera views ?
Can they be assigned to the keyboard NumPad for example ?
C:/Users/YourUserName/AppData/Roaming/Microsoft Flight Simulator/SimObjects/Airplanes/FNX320.
There will be 2 files, and 2 files ONLY in the FNX320 folder. State.cfg, and Cameras.cfg. If there are more, then you are in the wrong directory- likely in the actual sim install location where the Official and Community folders are. There is a similar folder structure there (SimObjects/Airplanes). That is NOT where you want to be.
If you’ve downloaded a custom cameras.cfg file, for the Fenix, follow the above directory tree, and drop the file in there to replace the existing cameras.cfg file.
How to access the views? It is the( EDIT) Left-Alt key and the 1 through 0 numbers at the TOP of your keyboard, and NOT the number pad on the right, if your keyboard has them.
Can they be assigned to the number pad? Yes but you will need to remap your keyboard via the sims control options.
EDITED: Left-Alt Key, Not Right- Alt.
Thanks for that Viper883
A clear and consise answer. It makes sense now 
Well I followed your directory tree to the letter (for Fenix) but there was only one file in there, which was the State.cfg.
So I copied the Fenix camera file (downloaded from fliightsim.to) into the folder with State.cfg, but using the right ALT key, it didn’t work 
Moved to Third Party Aircraft because this post concerns Fenix A320.
I have a small annoying problem with the Fenix 320 airbus.
When I move the camera to the overhead panel ( default camera or custom camera, does not matter), it starts flashing strangely for a moment … Can anyone tell me why this is happening. This does not occur with any other aircraft ??
Sorry my mistake! It’s the LEFT -Alt key. Don’t know what I was thinking.
Does not exist on my system.
Steam or MS store?
Look at the path in the explorer window. “costa2” is where your username would be. This is a steam install. If you are on MS store, it may be in a different location.
Store. xxxxxxxxxxxxxxx (to fill up the necessary letters for a post 
c:\Users\YourUserName\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\SimObjects\Airplanes\
Thanks. I found it.
It contains camera definition 0 to 9. I think those are the custom views. I’d like to change the fixed cockpit views, available in the camera menu under “cockpit”. Some of them are on the seats, but looking towards the front seat. They should also be defined somewhere.
PMDG 737 example.
Go to
Community\pmdg-aircraft-737\SimObjects\Airplanes\PMDG 737-700
in notepad open file named cameras.cfg