Secure the wheel into place

Place the nut onto the axle.

Grip the nut with the pliers.

Rotate clockwise until tight. There should be a tiny bit of space between the nut and the wheel.

Try not to tighten the nut too much or else the wheel may not spin effectively.

If one of your wheels still doesn't spin as well as the rest, check to make sure the bearings are fully placed in their sockets.