1. Open the Arduino IDE and then navigate to the Preferences screen by selecting the File menu, and then Preferences. Click the small button to the right of the text box labeled Additional Boards Manager URLs, and then paste the following URL into the windows which pops up: https://github.com/etherkit/ArduinoBoards/raw/master/package_etherkit_index.json
   Click OK to close this window, and then OK to close the Preferences.
2. Navigate to the Arduino Boards Manager in the IDE by selecting the Tools menu, then Board, and then Boards Manager.... In the search box in the upper right of the Boards Manager windows, type SAMD.
3. In the search results list below, find the entry for Arduino SAMD Boards, select it with your mouse, and then click the install button.
4. Next, find the entry for Etherkit SAMD Boards, select it, and click the install button. Close the Boards Manager window when this is complete.
5. In the Tools > Boards menu, you should now see Empyrean Alpha and Empyrean Beta listed as board options. Select the appropriate board in order to start uploading sketches to your Empyrean.

You can access the built-in USB-UART (virtual serial port) by using the SerialUSB object in your sketch, just as you use Serial in AVR-powered Arduinos. You can also use pins 0 and 1 of Empyrean as a hardware serial port with the Serial1 object.