For the Firgelli controller, the simplest way is to use the RC Servo Interface Mode. On the Control Interface (C3), you want to use these pins:
4 RC / Hobby Servo input signal
6 +5 Vdc power
On the Axon, just choose any digital port. Connect the servo signal pin on the Axon to pin 4 on the Firgelli board.
The Firgelli board requires regulated 5V, so pin 5 and 6 connects to ground and power on the regulated 5V analog power bus on the Axon.
J2, labeled BATTERY on the Firgelli board, connects to ground and power on the unregulated power bus on the Axon (where servos normally connect).
Word of caution:
The linear actuator you are using requires 5V on the datasheet, so I don't know what will happen if you use another voltage (it doesn't say). You have three options:
1) What I said above
2) You can either use an external 4.8V battery (keep grounds common!)
3) Use the regulated 5V to power the actuator, as the Axon can supply up to 1.5A and has thermal shutdown protection