It’s actually really easy to install this part, but if you did not build yours from a kit, or if it’s been a while since you had your printer apart, it can be daunting.
First remove the two M5x16r bolts on your MINI-z-top.
Pull the MINI-z-top assembly up until the two 10mm steel rods are free. Place tthe Mini-z-aligner over the middle bolt head.
Ensure that the notch in the mini-z-aligner fits over the middle bolt head.
Now simply place the two 10mm steel rods into the aligned holes in the mini-z-aligner and press down, the lead screw will slip into the center of the bearing.
Tighten up the two M5x16r bolts on your MINI-z-top and you are all done.