Tools you will need:

• 5mm hex key
• 2.5mm hex key
• 2mm hex key

Begin by loosening the clamp rings on the grips. Undo the screw in each one by one or two full turns using a 2.5mm hex key until the grip can freely spin on the handlebars. 

Your grip should now be able to slide off of the handlebar, and the end cap will also slide out with it. It may take a little effort to pop out the end cap.

Disconnect the brake cable from the handbrake. 
If the barrel adjuster on the hand brake is extended, you can retract it in two steps. First, thread the locking nut all the way against the end of the barrel adjuster away from the hand brake. Then screw the entire unit back towards the hand brake. 

Once the barrel adjuster is almost all the way against the hand brake, line up the slots on the barrel adjuster, locking nut, and hand brake.

When the slots are lined up, you should be able to pull the brake cable through the slots. Pull the brake cable housing away from the hand brake, then thread the cable through the slots. If you are unable to pull the cable housing out of the barrel adjuster, you can loosen the cable pinch bolt on the brake caliper and loosen the brake cable.

Squeeze the hand brake to reveal where the brake cable is attached. The end of the brake cable can sometimes rotate in its holder making it difficult to remove. Rotate it so that the flat side is facing up, and push straight upwards.

Remove the brake sensor from the underside of the hand brake assembly by removing the two screws with a 2mm hex key.

Loosen the screw on the bottom of the hand brake assembly by a couple of turns until the assembly can move freely on the handlebars, and remove the hand brake assembly.

Slide your new hand brake assembly onto the handlebars, but do not tighten it yet.

Reinstall the handgrip

Slide the grip onto the handlebar lining up the screws in a similar orientation to those on the right side. 

Press the end cap into place.

Tighten the two screws on the clamp rings until the grip can no longer spin on the handlebar.

Determine where the hand brake would feel the most comfortable and accessible while riding and tighten the screw on the underside using a 5mm hex key.

Reinstall the brake sensor on the underside of the hand brake using the two screws and a 2mm hex key.

Now, reattach the brake cable.

Squeeze the hand brake, and insert the end of the brake cable into its holder.

Thread the brake cable through the slots in the hand brake assembly, locking nut, and barrel adjuster.

Pull the cable housing and reinsert it into the end of the barrel adjuster. 

If you loosened the tension on the brake cable at the beginning by loosening the cable pinch bolt on the brake caliper, retention your brake by pulling the cable through and tightening the pinch bolt to hold it in place.

Readjust the barrel adjuster to fine-tune the tension of your brakes. The further away from the hand brake, the more tension will be on the brakes. Once the brakes are adjusted to your liking, turn the locking nut until it rests against the hand brake to hold everything in place.