Add a new latex class on Mac

1. need to have this folder

~/Library/texmf/

If not, try to make a directory , e.g. with this app

https://github.com/amunn/make-local-texmf

2. Download the .cls file, e.g. revtex4-2 from

https://journals.aps.org/revtex/revtex4-2-tds.zip

3. Put

.bib files into ~/Library/texmf/bibtex/bib/

.bst files into ~/Library/texmf/bibtex/bst/

.sty files, .cls files (and others) into ~/Library/texmf/tex/latex/