Install on MacOS: sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume.
Install on Linux: curl -L https://nixos.org/nix/install | sh.
Currently we use unstable channel of nixpkgs, enable it: nix-channel --add https://nixos.org/channels/nixpkgs-unstable.
Install configs: cd ./.config/nixpkgs && ./install.sh.
Install all packages: nix-rebuild.
To install other packages create your own overlay file in ~/.config/nixpkgs/overlays, see my-packages.nix for example.
Everytime you update overlay's files you need to run nix-rebuild command.
To update packages to latest versions run nix-channel --update && nix-rebuild.