Hi Bruce,
You should have been prompted to accept a Scan when you first started FMS Data Manager.
There are three tabs at the top. In Settings, make sure you X-Plane 12 path is correct.
In Addon Mappings , press Scan , then Save. Your X-Plane 12 and X-Plane 12 Addons should be detected. Press Save.
In Addon List select X-Plane 12 and X-Plane 12 Addons and press Update. In status bar at bottom of page, you should see the Updates occuring.
See also FAQ - Installing Navigation Data AIRAC Updates
Cheers
Ian