Firstly, ensure the wheel is properly clamped in place and your axle nuts or quick release is tight. Align each brake pad so that it contacts the braking surface squarely. Each side should look the same and be centred to the eye.

Loosen the cable pinch bolt on the caliper. Adjust the cable so that the brake pads are almost touching the rim. Tighten the cable pinch bolt.

Squeeze the lever and give the wheel a spin to check your work.

You will see a little barrel adjuster on the brake caliper. Fine adjustments can be made here.

The caliper itself can be adjusted to sit centrally. Often this can be done by hand.

Otherwise, loosen the clamp bolt at the rear of the fork and realign.

Once you are happy, make sure all the bolts are tight.