Hello! Iām totally new at this and obviously, I dont know anything.
It would be really helpful if you explain how to make an acapella version of a song on mac.
Thank you so much! 
You get one or more people to sing into a microphone without backing tracks or music.
Vocal Isolation of an existing song is a nice idea but there are no tools that do a reasonable job. You stand a much better chance of making a karaoke track, music without the vocals, but that mostly fails, too.
Taking apart a mixed song into instruments or voices in post production is difficult to impossible ā especially if you start with a ratty, compressed internet download.
Koz