Mobile Applications Designer is a GUI tool to create your mobile application. On the left side, there is a screens list. Mobile application mostly consists of its screens filled with widgets and triggers.
For every new mobile application, an authorization screen is created by default with prepopulated widgets and related actions to start from.
When you finished making changes don't forget to click the save button to save the mobile application schema. If everything goes wrong you can reload the page discarding changes or select previous versions of the mobile application schema.