Add the first step to clone.

Running-Mastodon/Docker-Guide.md

@@ -12,6 +12,11 @@ The project now includes a `Dockerfile` and a `docker-compose.yml` file (which r
 
 ## Setting up
 
+Clone Mastodon's repository.
+
+    git clone git@github.com:tootsuite/mastodon.git
+    cd mastodon
+
 Review the settings in `docker-compose.yml`. Note that it is **not default** to store the postgresql database and redis databases in a persistent storage location. If you plan on running your instance in production, you **must** uncomment the [`volumes` directive](https://github.com/tootsuite/mastodon/blob/972f6bc861affd9bc40181492833108f905a04b6/docker-compose.yml#L7-L16) in `docker-compose.yml`.
 
 Then, you need to fill in the `.env.production` file: