Updating to a newer version of nix

[allforabit]

Hi, I am following the instructions from here and have successfully got Nix to build and install. I'm very excited to use Nix on windows! However when I attempt to install packages I get the following error:

$ nix-env --install nodejs
error: evaluation aborted with the following error message: ‘
This version of Nixpkgs requires Nix >= 1.11, please upgrade:

- If you are running NixOS, use `nixos-rebuild' to upgrade your system.

- If you installed Nix using the install script (https://nixos.org/nix/install),
  it is safe to upgrade by running it again:

      curl https://nixos.org/nix/install | sh
’
(use ‘--show-trace’ to show detailed location information)

Is there any straightforward way to upgrade the version that's installed using the scripts here? Apologies, I am very new to Nix so I may be missing something obvious. I'm also aware that this repo is quite out of date and may not be supported anymore. I'm surprised I've managed to get this far with it to be honest.

Thanks very much!