The remaining longer cable in your AM1 kit is for the rear brake.
Remove the inner cable from the cable outer casing.
To assist with routing the cable outer casing through the frame, a preinstallation steel cable has already been threaded through the frame. Carefully remove the masking tape from both ends of the cable. DO NOT remove the cable from inside the frame.
The rear brake cable will be installed from the exposed end of the cable (circled). There may be a rubber cover over the end of the cable. If there is, remove this too. Still, DO NOT remove the cable from inside the frame.
Feed the cable outer casing over the exposed end of the preinstalled steel cable.
Carefully push the cable outer casing through the frame whilst making sure the preinstallation steel cable does not get pushed out.
Hold the end of the preinstallation steel cable whilst you push the rest of the cable outer casing through the frame.
Keep pushing the cable outer until it emerges out of the hole near the handlebars.
Once the cable outer casing is all the way through the frame you can remove the preinstallation steel cable. This can be placed into metal recycling. Be careful that the cable outer does not remove itself from the frame too!
Insert the cable outer casing through all of the clips at the rear of your AM1. Remove the clips and place the cable into the groove, then push the clip back over.
Feed the cable outer casing into the top of the disc brake calliper.
The cable outer casing should not have any extra slack at the back part of your AM1.
Pull the brake lever against the grip and insert the inner cable anchor into the receiver within the brake lever.
Next align the barrel adjuster and nut with the slot in the back of the brake lever.
Once the cable is in position release the brake lever and rotate the barrel adjuster so the cable can no longer fall out of the slot.
Thread the inner steel cable back into the cable outer casing.
Feed the steel inner cable into the cable outer casing until the cable outer casing reaches the brake lever.
Use the 5mm hex key to loosen off the cable clamp.
Insert the cable into the clamp.
Tighten the cable clamping bolt using the 5mm hex key.