To connect the LG CT Air Conditioning Ceiling Cassette to the Smart ThinQ App, first download the app on your smartphone and create an account. Ensure that your smartphone and the air conditioning unit are both connected to the same Wi-Fi network. Follow the in-app instructions to add a new device, select the air conditioning unit from the list of available devices, and complete the setup process. Once connected, you can use the app to control, monitor, and schedule the air conditioning unit remotely.