Occasionally the rear brake will need to be adjusted, either when your scooter first arrives or over time as the brake pads start to wear. If you hear friction / grinding when spinning the back wheel (and it does not spin freely) this means the brake needs to be loosened. If your braking power is too weak and the handbrake lever too loose, you'll need to tighten the brake.
The brakes can be adjusted in two locations. From the rear brake pad, or from the front caliper.
The rear adjuster (below) uses the same wrench size as was included in your original package. This is the best starting point for adjusting the brake, and is sometimes all that is needed to achieve the desired tension. Spinning to the right will tighten the brake by pushing the outer brake pad closer to the disc. Spinning to the left will pull the brake pad away from the disc and loosen the brake.
To further adjust the brake, the caliper nut below can be loosened using the same wrench. From here the brake cable can be pulled further through the bolt towards the back of the scooter for tighter braking, or loosened by letting some of the tension move forward through the brake cable. See the video below for more detailed instructions.
Full video here