The Malaga Airport parking location can be confusing, especially after the recent renovations. By building a new terminal, parking and runway they have increased capacity twofold, but it doesn't simplify matters for passengers. Answer: the green bus. This free service runs about every 15 minutes and will shuttle you from the arrivals hall to the various parking lots that are property of the airport. Ask the driver which lots are free (gratuito) and pay (de pago), as often this will mean a difference in security of those car parks.
If you are looking for a shuttle to your hotel or rental car, you should check with those companies before starting your journey. The hotel concierge (conserje) is normally the person to talk to with any doubts about where the shuttle pick up is and how to arrange it.