When you add a service, choose a Billing Frequency one-time or subscriptions — these can further be configured to hourly, daily, weekly, or monthly. The customer authorizes the recurring charge at checkout, and their card is then charged automatically on that schedule. You don't need to do anything after setup — payments come to you automatically.
Both sides stay in control: you can manage or cancel any client's recurring payment from your Projects tab or dashboard, and customers can cancel anytime. Customers are notified of upcoming or processed charges by in-app notification and/or email.
If a charge doesn't go through, see What happens if a recurring payment fails?