How to do automatic card authorization during checkout process?
Is this a Drupal 7 or a Drupal 8 site? That will impact the admin URL as noted below:
8: /admin/commerce/config/payment-gateways/
7: /admin/commerce/config/payment-methods/

You will want to edit the Authorize payment method, and look for "Default credit card transaction type" - that setting should be "Authorization and capture" as opposed to "Authorization only"