Nix macOS installing programs on system

I have setup nix on macOS ventura and using the nix command - so having to use flakes.

I can install programs using nix profile install -f hello - hello is in ~/.nix-profile/bin

But I can get a system configuration to install anything in home

I can’t find a minimal configuration on the net. The home manager document is nearly there but then in its flake refers to a non existent file configuration.nix.

The nearest was Setup nix, nix-darwin and home-manager from scratch on an M1 Macbook Pro · GitHub

I then found nixos-config/ at f6cea5013e67e0eb3b8f59e15f334711ebf1242f · MatthiasBenaets/nixos-config · GitHub
Which does if in darwin-configuration.nix install in /run/current-system/sw but noting in ~/.nix-profile

Is there a working simple complete configuration I can copy - only changing user or machine names that will put programs on the path in nix-defaults or will they only ever show in /run ?

Also what is the correct nix program.
The one in /nix/var/nix/profiles/default/bin/nix or one in /run/current-system/sw/bin