Assuming your MP3 or Wav is located in your Documents directory ( eg. /Users/jack/Documents/myfile.mp3 )
1- Download docker for mac: https://download.docker.com/mac/stable/Docker.dmg
2- After installation, open a terminal and type:
docker run -v ~/Documents:/Documents --rm -it researchdeezer/spleeter:conda-2stems separate -i /Documents/myfile.mp3 -o /Documents/