1st thing needed is internet access (you will need this on the boat as well). With Mac , there is no "APP", just the website "BoatyBall.com"

Go to https://boater.boatyball.com/signup and enter your information, including your credit card.

Alternatively, you can click on https://boater.boatyball.com/map and this will allow you to select a mooring field as well as a particular mooring ball and "Reserve' it.... (Actually at this point, it will direct you to login or sign in which can be done in the right top corner). Select/ reserve a ball.. After 4-5 minutes, if you have not put in your payment information, the ball will be released. (HINT, Try this reserve and NOT pay before you go and you will understand the process more).

Also, I see no reason to do the membership which allows you to reserve 24 hours before. Besides, the membership is only for 7 consecutive days (plus mooring fee). Easiest way to avoid worry about mooring balls is to get off sync with others. Seems Cooper is least busy Tuesday and Wednesday. Anegada ( and North sound) least busy on the weekends (when most charter boats are turning over).

I am down until March 16th on Sea Tiger, distinctive orange canvas and of course, a large Orange Clemson Tiger Paw.