If the PTT unit is between the transom brackets, tilt the motor all the way up to expose the fill port. Fill it to overflowing and replace the fill cap and cycle it down and up to bleed. Repeat a few times until there are no bubbles in the PTT fluid.
That motor shows 3 different power trim units. If the unit is mounted in the boat, trim the motor up and find the SS fill screw on the pump in the boat and fill to overflow.
PTT units are usually filled with Dextron II ATF, but also could have 5W-30 motor oil as well, so see what you already have in it.