The fill hole is a round head stainless steel screw. You have it right in the diaghram. Tilt the motor fully up and then fill. Originally the PTT held 5W-30 motor oil. Some subsequently used Dextron Auto trans fluid. See what you have in there and refill with the same.
Thank sr.Only remove the fill screw. Use a small funnel to introduce the PTT fluid. When she is full replace the fill screw.