If you need to prevent enrollment into Programs and Waitlists at full capacity and allow real-time reservation in the Enroll Form, you can do this with a check of a box! Here's how:
Head to My Company > Enroll Form settings
Check the box next to "Enforce enrollment capacities"
This setting also allows for real-time reservation in the Enroll Form to prevent over-enrollment into your Programs. See this support article to learn how real-time reservation works.