Once an order has been placed from the B2B Store, its status will be "Pending validation":
You can Edit the order to make any changes, add a discount or shipping costs for example. You can send it back to the customer if needed. Once you are ready, click on "Validate" to validate the order:
If you want to validate each order automatically, you can activate this option in the the B2B Store Settings.
B2B Store > Settings > Setup
To find out more, please visit this page.