1. Park your car in a safe location and turn off the engine.
2. Open the hood of your car.
3. Locate the vacuum actuator. It is usually located on the passenger side of the engine compartment, near the firewall.
4. Disconnect the vacuum hose from the actuator.
5. Remove the bolts that hold the actuator in place.
6. Remove the old actuator and install the new one.
7. Reinstall the bolts and connect the vacuum hose.
8. Close the hood of your car.
9. Start the engine and test the air conditioning or heating system to make sure that the blend door is working properly.
If you are not comfortable performing this repair yourself, you can take your car to a qualified mechanic.