...
pcsd = {
  # This way of declaring inputs is way cleaner IMO
  type = "github";
  owner = "matt1432";
  repo = "nixos-pcsd";

  # Here is the classic one
  # url = "github:matt1432/nixos-pcsd";
};
...

{pcsd, ...}: {
  imports = [pcsd.nixosModules.default];

  services.pcsd = {
    enable = true;
    enableBinaryCache = true;

    # I highly recommend using sops-nix or agenix for these settings
    corosyncKeyFile = builtins.toFile "keyfile" "some128charLongText";
    clusterUserPasswordFile = builtins.toFile "password" "somePassword";

    nodes = [
      {
        name = "this Machine's Hostname";
        nodeid = 1;
        ring_addrs = [
          # This is where your machine's local ips go
          "192.168.0.255"
        ];
      }

      # the other nodes of your cluster go here
    ];
  };
}