In the following example, we are assuming that your Emacs files are stored in ‘~/.emacs.d’ and that you want to place the Modus themes in ‘~/.emacs.d/modus-themes’.
$ git clone https://gitlab.com/protesilaos/modus-themes.git ~/.emacs.d/modus-themes
(add-to-list 'load-path "~/.emacs.d/modus-themes")
The themes are now ready to be used: Enable and load.