Here you can find the answers how to Getting Started with Apple HomeKit and Yale.
You can add your lock to your HomeKit Home through the Yale Access App or directly in the Homekit App. This will let you control the lock via HomeKit as well as add it to a HomeKit Scene. To Set Up In Yale Access App
You are prompted to enable HomeKit during the initial lock setup process. If you do not choose to enable HomeKit during setup, you can enable it later through the Yale Access App.
PLEASE NOTE - If you are finding that the app is unable to detect your lock when setting up HomeKit in the Yale Access App you can perform a HomeKit reset by pressing and holding the red button on the back of the lock for 5 seconds. Retrying the process should get you going.