do you mean splitter? under the front bumper
or
rear spoiler on the roof above rear window?
if splitter, it was probably screwed on, so undo these.
was not designed to go on the bumper type you have, based on sig pic, so had to be attached by other means.
for rear spoiler, need to remove inner boot lining to get at the screws, undo and remove. a few guides on advise to do this kicking about