This is tricky to describe it only in words. I do have an instruction video, but that is in Dutch.
To assign regions to geocaches (e.g. State, Municipality or other), you need to have shapefiles added to GAPP.
Shapefiles can be found at e.g. http://www.gadm.org/download
Shapefile of Germany can be downloaded by GAPP. Go to Plugins->Settings->Shapefiles
Press Download (I think) and you get a list of Shapefiles that are served by Globalcaching.eu.
But again, you can download any shapefile and install it by using the same settings screen.
Within the shapefile you have to set the region (country, state etc), the coordinate system (most likely WGS84), name field (check the csv file if available for the name field to use. If it is not present, just try them all)
If you added shapefiles within the settings screen, save the configuration and the shapefiles are loaded.
To check the shapefiles, go to Google Map window
There you can select a region (country, state etc)
Then select the name (like name of the State)
The shape (boundery of the region) will be drawn on the map.
If you think the regions are ok, then you can use the Assign regions to geocaches.
GAPP will calculate in which region the geocache is located and assigns it to that region.
I hope this answer helps a bit.