Most people don't use their boats/motors during the winter months so it's highly recommended you winterize the boat and motor when you feel you are no longer going to use it until the next year. Just don't wait month's or until after the first freeze, that may be too late.
Anyway, it's recommended you change the LU lube every fall as part of the winterizing of the motor. There are two plugs in the LU. One is on the side and one is on the bottom part of the rounded section for the prop shaft. Remove both plugs with a pan under the motor and trim the motor until it's trimed out about 10 degrees, that's so all the lube can drain out better.
Forgot, before starting the project, go by Wally World or you dealer and get one of those $10 pumps that go in a quart bottle of lube, makes life much simpler since you've never used squeeze tubes.
If it's a new motor, still under warrenty, I would get the factory brand recommended for the motor. If warrenty is not and issue, I would go by a parts store and get some Valvoline 100% Synthec 85 - 90 Gear Lube. Screw the end on your pump hose in the bottom hole on the LU and the pump into the bottle of lube. Trim the motor until it's sitting vertical and fairly level. Start pump lube into the bottom hole until it starts to come out the top hole. Quit as soon as it starts to come out, put the plug in the top hole, trim the motor up so the bottom plug is much easier to get too (your not on your head trying to get the dang plug started), screw the hose out and screw the bottom plug in.
You also need to go through the rest of the winterizing, Fogging the motor, greasing all fittings, adding stabalizer to fuel tank, purging the fuel system. Then if the boat is in a freezing climate, it needs to be winterized also
More than you ask, got a little long winded.