In order to join SAPSA, you need to join a recognised shooting club, through your local province. Each province administers their own clubs.
Simply determine in which province you are domiciled, then contact the provincial practical shooting association to ascertain where your nearest practical shooting club is. Contact the relevant club chairman or club representative for an appointment to join. This will most probably be at the shooting range when the club next meets for a match.
Here are the details of the different provinces and affiliate organisations: