This process requires first importing these orders into the system as Open Orders, and then processing them via the process order import.
1. You need to have a CSV file with the order information.
2. Use the order import to import the orders into the system.
3. Use the same file in the process order import to process these orders in the system.
Please note! Since these orders will be initially imported into the Open Orders screen, they will reserve the available stock for your SKUs in the system. And when they are processed, they will also deduct stock for their linked items. If you are already using the system for inventory management, and these are historic orders which are not supposed to affect your current stock levels in the warehouse, then the best approach would be to process them from a different 'virtual' location in the system. That location will not be enabled for your channel inventory sync, so it will not affect the total stock submitted to channels. Your stock items will not have any levels in this new location, so no stock will be deducted either.
1. create a new location in the system
3. when using the process order import, specify this 'virtual' location the column mapping step again.