the race is the track the bearings run in, when you remove all the balls, there are two rings, one in the top and one in the bottom, knock them out with a hammer and a piece of hardwood, they'll look like a ring with a rounded inside edge. if you have them out already, and the new bearings don't fit, check the dimension with a dial caliper, the inside dimension of the neck should be almost exactly what the outside dimension of the bearing is. if it's not, first make sure you don't have the top and bottom bearings mixed up, if this isn't the problem, you ordered the wrong bearings
if the dimension is ok, but they're just tight, then use a piece of hardwood and a hammer to knock them in, place the bearing on the neck, place the hardwood flat over the bearing, and gently start to drive it in, if one side is higher, tap that side more, you'll get it in if you do it carefully