Filip Höfer chess software supports opening games in the Portable Game Notation (PGN) format. Great games in the PGN format can be downloaded from many sites including:
The Week in Chess Magazine - new master games in PGN every week.
A very large collection of master games and openings.
Chess games database and community.
Note that some of the downloads are zip files. To get PGNs out of a zip file, simply right-click the file and select Extract all.
The PGNs can be opened in Chess 2020, Chess 2013, or Chess 2012. Go to the File menu and select Open...