Step 1 - Remove Wiper Blade
Raise the wiper arm off the screen, then remove the wiper blade away from it by pushing the locking tab inwards. Keep hold of it while you move the blade and holder towards the bonnet.
Step 2 - Remove New Wiper Blade from Packet
Remove the new wiper blade from the pack and make sure it is the right way up (use the remaining wiper arm to compare).
Step 3 - Replace Wiper Blade
Replace the blade but keep hold of the arm. This is pretty much the reverse of how you took it out, when you put the wiper into place it should cick together.
Step 4 - Lower Wiper Arm
Lower the wiper arm so it sits nicely at the base of the windshield. Once lowered make sure your wipers are working correctly and clearing the windscreen as they should.