The o-rings go on the top and bottom of the hollow balls. So slide one on to the base, attach the shock then slide on the other o-ring. You see that one of the hollow balls are larger than the others, one fits in the top of the shock and the other in the lower. Not sure which one without pulling one to bits.
I don't always use the o-rings on the bottom of the shocks. They can become a little tight for my liking.
Hope this helps.