Heres the procedure below:
When adding coolant, it is important that you use GM Goodwrench DEX-COOLTM coolant. If coolant other than DEX-COOLTM is added to the system, the engine coolant will require change sooner: at 50 000 km (30,000 miles) or 24 months.
On vehicles equipped with the 3.1L engine, open the coolant air bleed valve. The coolant air bleed valve is located on the top of the thermostat bypass pipe/heater pipe assembly. Close the valve once a continuous stream of coolant is expelled from the valve.
After servicing the cooling system, and if the vehicle is equipped with an intermittent low coolant light, an occasional low coolant light may be encountered during some extreme driving maneuvers. This complaint should be eliminated by removing the surge tank cap and adding coolant to a level just at or above the full cold line when the system is cold.
Ok, real simple. Engine cold. Open bleeder. Fill with coolant until all water is coming out bleeder. Close bleeder then do the procedure below: