You can take payment in 4 ways.
The first way is to have your customers book themselves via the 'Checkout page' and pay at the time of booking. To share this checkout page with your customers > click Appointments > Schedule > Checkout -- copy the URL to share it.
Or, you can book appointments for your customers and take payment in one of three ways:
click the appointment & email a payment link to the customer
clicking the appointment, click the 'Pay' button to take payment
open Point of Sale, select the customer, and choose Appointment (it will show any unpaid appointments they have to their name)
See all of the above in action and learn more here.