Your going to have to be more specific with the brand, horsepower and what type of trim you have. All outboard trims are filled while the motor is in the fully raised position but it depends on the brand and size.
How To Add Fluid To A Hydraulic Trim Motor On A Boat?
My 1990 johnson 60 horse power wont tilt up unless some helps me lift it up so I decide to change the oil, I found it had some water in it so I replaced it, but it still wont lift.