You will need to purchase a wiper blade. I used the H772 wiper blade from Halfords
Raise the rear wiper arm on the car
To remove the rear wiper, lift the bottom part and insert your finger behind, then pull away from the arm. The central pin will disconnect from the arm. This is the central pin that clicks into the arm
Reinsert the new wiper blade into the housing that holds the wiper arm. It's on a spring that wraps around the central pin. Use the small recess gaps at the edge of the wiper arm, and align it with the pin on the blade
The wiper blade when fitted correctly should audibly click, and require a slight amount of force to insert. It will be almost flush with the arm.
The first picture shows the blade fully inserted, the second picture is when the blade hasn't been fully inserted, and requires to be pushed in further into the wiper arm.
When the wiper arm is installed correctly, it will look like the above. The 2nd picture is what the wiper arm looks like when correctly installed.
The last picture is when the wiper arm has been installed the wrong way around, simply turn the wiper blade 180 degrees and reinsert