The FMS Data Manager is used to detect addons and install navigation data (AIRAC) in the correct locations. Do you have any issues with this process? It should find your AS12 installation and allow you to update its data automatically.
If FMS Data Manager is not able to automatically detect your AS12 installation, you can add it manually by following these steps:
In the last step, the “Default folder” option should work. If it does not, perhaps this topic could be interesting as it shows both a solution to a potential issue and what location you can expect to install your AIRAC into (HiFi\ASXP\NavigraphData\ASXP):