All add-ons for MSFS should be installed into the Community root folder. Aircraft add-on installers will attempt to find the Community folder by reading the UserCfg.Opt file. By default the location of the Community folder will depend on which version of MSFS you are running.

Windows Store default location:
C:\Users\[Your User Name]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages\Community

Steam default location:
C:\Users\[Your User Name]\AppData\Local\Packages\Microsoft.FlightDashboard_8wekyb3d8bbwe\LocalCache\Packages\Community

or it might be here:
C:\Users\[Your User Name]\AppData\Roaming\Microsoft Flight Simulator\Packages\Community

If you have a custom install location then you should ensure that the installer points to the correct location before continuing.

If you still cannot find your Community folder you can read the location from the UserCfg.Opt file. This file can be found at either:

Windows Store location:
C:\Users\[Your User Name]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\UserCfg.Opt

Steam location:
C:\Users\[Your User Name]\AppData\Roaming\Microsoft Flight Simulator\UserCfg.Opt

Load the file into a text editor and look at the last line which should be the "InstalledPackagesPath".

Scenery add-ons should be unzipped and then the contents of the Community folder in the zip manually copied to your own Community folder.

Installing into the program directory:
Run the aircraft installer and select the P3D v4 install to program directory option. Manually change the install directory from Prepar3D v4 to Prepar3D v5. You will need to install the aircraft once for v4 and once for v5 if you use this method.

Installing outside the program directory:
Run the aircraft installer and select the P3D v4 install outside program directory option. Select the location where you want to install the aircraft (by default this will be the P3D v4 add-ons folder and you can still use this if you have P3D v4 also installed). When the installer runs a batch file is run to update the add-on location in both P3D v4 and v5. You should only install the P3D v4 version outside the program directory once for use in both P3D v4 and v5. The installer updates the location of the add-on in both P3D v4 and P3D v5 as it has already been setup in expectation of the eventual release of P3D v5.

If you already have the aircraft installed outside the program directory with Prepar3D v4:
Either re-run the installer and reinstall the aircraft to the exact same location. Or, go to the location that the aircraft is installed and run the P3D_install.bat batch file found in the aircraft folder (other files in that folder will be the Content folder, add-on.xml and readme.txt).

The P3D_install.bat batch file is already setup for use with both Prepar3D v4 and Prepar3D v5. This batch file updates the add-on location for both P3D v4 and P3D v5. You should only install the P3D v4 version of the aircraft once if you are installing it outside the program folder and it will be available for use in both simulators.

Unfortunately a number of flightsim stores have closed business lately. Any customer who is unable to download any Ant's Airplanes products should contact me (support@antsairplanes.com) with details of their orders (product(s) bought and the order number). I will then happily be able to provide these customers with new download links via SendOwl.