Remove the plastic cover of the back fork on both sides of the fork (2 pieces, 1 per side) by peeling off the sticker so that the screws can be loosened.
Loosen the caliper mounting screws
Loosen the brake caliper
Loosen the back rim splash guard screws and mounting screws (Screws under the reflective sticker)
Loosen the back rim mounting screws
Remove the tyre
Below is information on how to replace the inner tube.
Remove the tyre from the rim using a tyre remover used for bicycles
Remove the broken inner tube
Check that there is no dirt under the outer tyre
Put the new tube in the correct place
Lift the tyre into place - you can use tyre removers to help
Fill the tyre properly with air
Below is information on how to replace the tyre.
Fit the back rim in the right place
Center the disc brake so that it is a little free on both sides between the brake disc and the brake pads when you do not press the brake - you can use e.g. a piece of cardboard or a mobile phone flashlight to help
Tighten the caliper mounting screws
Screw in the back fender mounting screws
Attach the back fork's plastic cover