You will need your frame (AM1 or AM1 STEP) and your fork with the brake installed as explained in step 2. Note this is the same process whether you have an AM1 or the AM1 STEP.
You will need the tapered washer (left) and crown cap (right) from your AM1 build kit.
Insert the fork through the headset of the frame. These steps are much easier if you use a bike stand or ask someone to help you.
It will insert without resistance.
Now push the tapered washer onto the fork. The correct direction is shown in the image above.
Push the tapered washer down to be completely flush with top of the frame.
Take the crown cap and place this over the top of the fork. This has a rubber seal inside to stop water getting into your AM1. So it is a bit harder to push down onto the top of the frame, but it is very important to push it all the way down.
Push the crown cap down until it is completely flush with the frame. Now set the frame and fork to one side.