From the owner's manual:
(1) Fill the fuel tank with fuel, and open the fuel cock.
(2) Open the bleeding screws at the top of the filter with
two turns.
(3) When bubbles disappear from fuel coming out of the
plug, tighten the bleeding screws.
(4) Open the air vent plug on the fuel injection pump.
(5) Pull the throttle lever completely to stop the engine,
and start the starter for about 10 seconds.
[CAUTION]
• Be sure to pull the throttle lever back
completely before cranking the starter.
(6) Close the air vent plug when air bubbles disappear from
the fuel flowing out.
I have also found it advisable to add a 7th step:
Push throttle lever forward to idle position. Loosen each of the fuel pipe connections at the injectors. Crank starter until air bubbles disappear from the fuel flowing out. Tighten each connection in turn as the bubbles stop. But that is not in the manual.