Simply drag and drop the GeoPackage or Shapefile into your workspace. The coordinate reference system (CRS) is standard WGS84 (longitude/latitude) . Key Considerations

Click the Map tab, select Add Data , and navigate to your GADM 3.6 file.

Once downloaded, you can integrate GADM 3.6 into your preferred analysis environment:

Version 3.6 introduced GeoPackage as the standard format, though Shapefiles and RDS remain available. To help you get the right files, Download GADM data

A Complete Guide to Downloading and Working with GADM Data Version 3.6