Remove the window trim that goes around the top, there are 3 screws that holds the spoiler on (two 10mm bolts outer and one torq screw in the middle). There's 3 torq screws in total but the other 2 hold the LED brake light on, so this is worthwhile removing too to get it out of the way.
With all 5 screws/bolts removed the spoiler will still be stuck on with very very strong double sided tape. I removed one by using a very wide thin scraper and slower hacking down the back the spoiler taking care not to damage it of course. It takes a bit of time and it clings on forever!!