FiField Bonfire Owner's Manual page 15

6. To set the wheel in place line up the rectangular piece of the
bearing with the corresponding rectangular slot in the fork (as
shown below). Gently press down on the wheel until it falls
snugly into place. You may need to pull the fork apart slightly if
you cannot get the wheel to fit properly with constant easy
pressure. A proper connection is shown below.
7. Place the washer over the bolt, followed by the lock washer, and
finally tighten the nut to secure the wheel properly. Use a 15mm
wrench to tighten. When both nuts are fully tightened, return the
bike to its original upright position and put the kickstand down
for the remainder of assembly.
11