First, install Nix if not installed yet:

curl https://nixos.org/nix/install | sh

(See this comment for how to install Nix on macOS Catalina.)

Next, install Home Manager:

nix-channel --add https://github.com/rycee/home-manager/archive/master.tar.gz home-manager
nix-channel --update

And then do:

ln -s `pwd` ~/.config/nixpkgs
nix-shell '<home-manager>' -A install

You might not want to expose SSH config files or something like that into the public repository because doing so would put your precious servers at potential security risk. So .dotfiles/private is reserved for private information. Clone your own private dotfiles respository to private. private-example shows an example.

Place host-local configuration files in local. See local-example for an example.

It's recommended to define home.{stateVersion,username,homeDirectory} (required starting from Home Manager release 22.11) in local/home.nix.