HI.
Dont know the exact procedure for the Golf. However, in my Polo and Octavia, the procedure is pretty much same and the Golf shouldn’t differ much.
Open the trunk lid.
Locate any possible screws and remove them (it might not have any…)
Remove the plastic cover, its held in place from the inside with very strong clips, you might think that its going to brake.. It wont, but be careful anyway. Get some interior disassembly tools, it will make all the difference in the world.