The Campaign Monitor integration works right out of the box with Yieldify. To integrate, simply go to the Settings page of the platform and hit Connect. You'll then be presented with an authorisation screen:
Once connected, you'll be redirected back to the Settings page where you'll need to add a list ID.
In Campaign Monitor, you can find the list ID by going to Lists & Subscribers > Selecting the list you want to send leads to > Clicking Change Name/Type > Selecting the API Subscriber List ID.