With the introduction of the Arduino IDE 1.5, there were several under-the-hood changes that affect how 3rd-Party boards are added. No problem though, follow these steps:
1. Create a new folder called "macchina" in the "variants" folder found here:
2. Download the attached "pins_arduino.h" file to this folder. This file tells the IDE that the Macchina has some extra pins compared to the Mega. Make sure this file reads exactly as "pins_arduino.h".
3. Lastly we want to add Macchina to the boards file. To do this, open up the "boards.txt file found here: Arduino\hardware\arduino\avr\boards.txt
Paste the following to the end of that file:
That's it! Open up the Arduino IDE, and you should see "Macchina" under the list of boards.
To verify that everything is set up correctly, try out the "Blink" example found in: Files>Examples>0.1 Basics>Blink.
Change the LED to one of the on-board LEDs on the Macchina like this:
Pin 81 corresponds to the "CAN TX" LED on the Macchina, Pin 82 corresponds to "CAN RX"
Upload a sketch, and you should be good to go!