Updated README.

README.md

@@ -10,6 +10,10 @@ Clone this repository. Then, install the dependencies.
 npm install
 ```
 
+## Configuration
+
+Inside the `data` folder there is a `credentials.json.example` file. Rename this to `credentials.json` and fill it up with your own credentials.
+
 ## Usage
 
 You can use the script with the following command: