Before starting the repair, switch to the highest gear to get the chain in a favourable position for removing the tires.
There is an easy way to get the tires out if you push back the chain holder on the back tire.
On the front wheel, be sure to remove the cable of the dynamo by removing the cap on the wires.
Before putting the new brake pads in, push the cylinders inside the casing in to make space for the pads. Otherwise it will be hard to get them in.
Don't use the brake while repearing to avoid getting the cylinders stuck.
The brakes will not work after changing, use the breaking handle a few times until there is some resistance. DO NOT get on the bike before that, you will hurt yourself!