The photos show a front hub, but a rear hub is the same concept.
Retainer-side first, using the old bearing to get it in place. Don't hammer the inner races!
Then put your retaining ring back on... and get the original stakes to line up. Make sure to punch new ones when you're finished!
Spacer... Make sure the NARROW END goes on the RETAINER SIDE. This photo shows the WIDE END.
Use the old bearing to get the new bearing to seat flush, to start.
NOW AN IMPORTANT PART.
Don't drive that bearing too tight! You want the inner spacer to be able to move, ever so slightly, but not too loose either!
The little sliver of silver you see in the center here is the opposite side's inner bearing race.
This means that the spacer moves, still (it was loose at this point). Notice in the pic above of the spacer that it isn't a super tight fit in the hub. It can move vertically (wheel upright as if on bike). You don't want it moving side to side, though, as that is too loose. It is all by feel...
How I found the magical "Just RightTM" position for this floating bearing is that it should be tight enough so that the spacer doesn't move side to side (remember wheel in normal, riding position... up or down is OK), BUT you should be able to spin both bearings freely, in opposite directions, at the same time, independently of the spacer. You may find you can feel the inner race rub ever so slightly on the spacer at this point. It takes a bit of feeling around (use your pinky's, those are small holes on the front wheel!)... but you'll get it. If you do make it too tight the first time around, GENTLY tap from the retainer side on the INNER RACES. GENTLY GOING SLOWLY, ALL THE WAY AROUND, WITH A BRASS PUNCH AT LEAST 1/4". Eventually you will get the floating bearing moved outwards a bit, and then you can try again. Ask me how I know... I thought I was done for, when I did it too tight... but I went and checked HondaMan's book, and this is what was recommended.
Then reassemble everything!