Download the MP3 audio files from jw.org and rename them to 001.mp3, 002.m4a, ... and put them into the audio folder.
To import the lyrics in your language download the two epubs from jw.org (the song book and the new songs). With SongScreen open click on the "Settings" button and there click "New language...". Then simply follow the instructions of the language editing assistant.
To deploy execute the following in a terminal
pyinstaller SongScreen.spec
Of course you need to install PyInstaller first.
To enable high resolution rendering on MacOS you have to find the Info.plist file in the application package and add the following lines
<Key>NSHighResolutionCapable</key>
<String>True</string>