To check the PS fluid, open your engine compartment and remove the PS reservoir cap.
The inside of the cap will have a stick with marks for cold/hot. I like checking when it's cold and ensure the fluid is at the mark. No more no less.
A quick search yielded this:
- Open the engine compartment
HOW TO: Access Engine Compartment on my Porsche Boxster - GSR Autosport Community
Accessing the Engine
- PS fluid reservoir location (same for 986)
Where to top up Power Steering fluid? - 987-1 Series (Boxster, Boxster S) - RennTech.org Forums