It opens and closes automatically tied to the speed of the car. I think this is covered in the manual.  You can also test the spoiler, again procedure is in manual.
Good luck!
HI everyone !
I am a new user. I have got a 2003 Boxster s with carrera 18" wheels (photos soon)
Ive got a question. How to open the rear spoiler in my porsche? 
 
 
Best regards.