To initialize the SDK you have to create a token through the dashboard.
Click on the settings icon on the top-right and create an API Key specifying the permissions.
On your app before doing anything you must initialize the SDK with your API Key by using the MBurger class, also you should specify if you are using the development api or the standard API, be aware that different mode means different key, so a "development api key" would not work if you are using standard api.
MBurger.initialize("<Your API Key>",<Development mode>);
MBurger.initialize() also may accept other parameters to control if you want MBurger SDK to cache your requests, you will find all information you need inside the Javadoc. Requesting anything from the SDK before initializing will result in an exception, so you shoud initialize on your onCreate starting Activity or on your custom Application class.
Basically you can obtain and use all your project data using 3 classes with public static methods: MBurgerTasks, MBurgerMapper and MBurgerApiActionInitializer. All these classes are used to obtain and map your custom objects from MBurger objects.