From Wikivoyage, you have a few options:
The light rail system serves the airport.
Bus AP1 plies a route between the airport and the Barrier Gate. Its route passes through several points on Taipa Island, and it stops at the ferry terminal on the peninsula on the way. It costs MOP$4.20 per passenger, MOP$3 per bag. It has limited provision for baggage, and can be very crowded (you may not even get the first bus to arrive). Change at the ferry terminal for other destinations, the frequent number 3 bus runs from the ferry terminal and passes the Lisboa, Landmark Hotel, and Holiday Inn, or catch one of the hotel/casino shuttles which go the ferry terminal. The buses do not give change, but there is a currency exchange just inside the terminal that will change foreign currency into low denomination MOP.
Alternatively, take a metered taxi straight to your destination, but there's a MOP$5 airport surcharge plus MOP$2 for the bridge and MOP$3 per bag. Fares to the city center are around MOP$40–50, the trip taking 15–20 minutes.
For anyone else reading this, if continuing on to Hong Kong, use the Express Link from the airport, however be aware it only runs from 11am to 6pm.