Application pin configuration are based on the pins already predefined inside a board configuration.
Using the <CTRL>+N, or the File/New menu option, you'll be able to access the "Creation of a pinmap configuration from an existing board" wizard. You will be asked to enter a file name (with extension set to .gpio), then choose the board you want to use, from the list of predefined boards.
Choose the board to start from. Again if the project has not yet been converted to Xtext you must do it. This step is mandatory, as the configuration is based on the Xtext technology, declaring the project as an Xtext project. It allows for launching the appropriate editor when double-clicking on the configuration.
Now your project is ready and open in the editor area of the tool.
Here is the content of the pin configuration, whenever you've chosen the myPredefinedBoard.gpio_board file in list of available boards in the previous step.
Now you can start adding pin configurations to your application.