Jack,
I'm not sure what your Wheel's look like but I expect they all have the same style of cap covering the lugs.
Remove the cap from the wheel... you should be able to see the dust cover for the axle... if it's like mine... there is a black plastic plug in the middle of the steel dust cover for the bearings. Pry that plastic cover out... look inside... There should be a Zerk grease fitting there.
Marv