When you have reached the appropriate point in your site workflow, you may use the session to perform an operation using the card details collected in the session. It is entirely at your discretion when this is done. It may be at the point of collecting the card details, or at a later stage if you require additional pages to be displayed.
For example, you may wish to display a Payment Details Review page so that the payer has the opportunity to review all of the details of their payment before they commit to the payment.
The operation request using a session is exactly the same as that of the equivalent DirectAPI operations using card details with the only difference being that a session identifier is specified in place of the card details. For information on operations that reference a session, see Using a Payment Session.