not hard at all. When you get them and you offer them up, you will see that the spoiler is facing the wrong way, so it will actually lift the wiper maybe.
From memory, you un clip the end caps then slide the first half of the spoiler, then the arm mount, then the other half of the spoiler. Spin em round and then slide them back on and clip the end cap back on, job done.
I did think the Tesco flat blades were brilliant until one folded back on itself whilst in heavy rain. It turned out it was my fault, as I did not click them in properly. There is a little end cap swing cover on the arm mount, make sure that is shut and stays shut. If it keeps flopping open, it means you have not located the wiper properly.
It has not flown off since and they wipers perform brilliant. The dont clear the passenger lowest corner, but its not a problem.
Dem, this could be your big entry into DIY on your car.....go on, its easy!