Update usage README

README.md

@@ -1,8 +1,15 @@
 # godot-ci
 Docker image to deploy Godot Engine games
 
-## Usage example
-A `.gitlab-ci.yml` is included in this project as a usage example.
-
-##### Docker Hub
+## Docker Hub
 https://hub.docker.com/r/barichello/godot-ci/
+
+## Usage example
+A `.gitlab-ci.yml` is included in this project as a usage example.<br>
+After adapting the paths and names according to your project needs you will need the following **Variable** set in GitLab for this image to work:
+
+|Variable|Description|Example|
+|-|-|-|
+|$REMOTE_URL | The `git remote` where the web export will be hosted (in this case GitHub), it should contain your [deploy/personal access token](https://github.com/settings/tokens)|`https://<github username>:<deploy token>@github.com/<username>/<repository>.git`
+
+Others variables are set automatically by the `gitlab-runner`