These are the components required to install the rear rack. There are 4 short bolts with 4 washers and a long bolt with a spacer. You will only require 3 short bolts with washers and the long bolt with spacer.
Start by screwing two bolts on the two mounting holes on top of the seat stays using the 4mm hex key. Do not tighten them fully as you need a bit of play to adjust the rack.
Tighten the two bolts on the dropouts using the 4mm hex key. For the AM1+ and AM1 STEP+, use the long bolt and the long spacer on the disc brake side (as shown int he pic above). Use the short bolt on the other side. Do not over-tighten the bolts to avoid stripping the threads.
Tighten the two seat stays bolts fully. The rack will adjust itself when you tighten the bolts. Do not over-tighten the bolts to avoid stripping the threads.