You will need a USB mini-B cable. Attach the mini-B connector to the Akafuino X, and then attach the other end to your computer.
The first time you connect the board, your computer will assign a serial port.
On OS X, the serial port will typically look like this: /dev/tty.usbserial-A700ft5E
On Linux, the serial port will typically look like this: /dev/tty.usbserial-A700ft5E
On Windows, the serial port will typically look like this: COM5 (Windows users must download the FTDI drivers from the FTDI webpage: here)
Setting up the Arduino IDE
The Akafuino X uses a special version of the Arduino IDE that has support for the XMega line of processors that the Akafuino X uses.
Get it from the download page at GitHub:
Using the Arduino IDE
Once the Akafuino X has been plugged in, open the special version of the Arduino IDE you set up in the previous step.
Go to the Tools -> Serial Ports menu, and you should see the assigned serial port there. Make sure that it is selected.
Now go to Tools -> Board and select "Akafuino X"
You are now ready to upload a sketch: Select File -> Examples -> Blink and press the Upload button in the toolbar. Once the upload is complete you should see the user led blink.
Make sure you select the correct board type in the Tools -> Board menu. Once that is completed, you can use the upload button in the toolbar to upload your sketch.
Usage as a Debugging Port
Anything you print using the Serial library in Arduino will be printed to the serial port on your computer.
Now, anything you print using Serial.println will be sent through the FTDI adapter and to your computer. Click on the Serial Monitor button in the IDE to see the output. Make sure it is set to 9600 bps.