Update readme

readme.md

@@ -1,9 +1,34 @@
 # Pleroma on NixOS: OTP Release
 
+## How to Use?
+
+To use this module on your NixOS system, you'll first have to download
+it and include it in your import list.
+
+```
+{ config, pkgs, ... }:
+let
+  pleromaModuleSrc = builtins.fetchTarball {
+    url = "https://git.alternativebit.fr/NinjaTrappeur/pleroma-otp-nixos/archive/master.tar.gz";
+    sha256 = "1rv2m8wg8nkz2cd1i8x7kdwabxxcx73q5w4lq9sgv23z52g4x3bh";
+  };
+in {
+    imports = [
+        "${pleromaModuleSrc}/modules/pleroma.nix"
+    ];
+}
+```
+
+Note: while this will work just fine, I'd recommand using
+[niv](https://github.com/nmattia/niv) to perform this kind of external
+source tracking. It's much more convenient to maintain on the long
+run!
+
 ## TODO
 
 - Add NixOS module.
 
+
 ## Minor Annoyances
 
 We're retrieving the binary distribution directly from the GitLab CI pipeline.