When you add a price on some content, new buttons for purchasing are available in relevant places, e.g. in the Course Browser for courses.
In the course info, users will see the total price and discounts for that course. If they're interested, they can add it to their shopping cart.
In the Shopping cart, they can overview their order details and finalize the purchase. They may need to accept the Terms & Conditions, if those were set up on the environment.
Before payment, they can see whether the taxes will be added to the total price, and which discounts will be applied.
After clicking Proceed to payment, users are transferred to the payment system.
If the transaction is successful, the course will become available to the user.