Manual orders are useful when a retailer needs to do the following tasks:
Accept payment for an order that you make over the phone, in person, or elsewhere. When you accept payment for your draft order, an order is created for it on the Orders page.
Send invoices to customers to pay with a secure checkout link.
Use custom items to represent additional costs or products that aren't displayed in your inventory.
Manually re-create mistaken orders from any of your active sales channels.
Sell products at a discount or wholesale rates.
Take pre-orders.
Here are the guides on creating manual orders:
Shopify: Creating draft orders
BigCommerce: Creating a Manual Order
WooCommerce: Manually Adding an Order
Once all these steps are followed, the system should create an order which then gets sent off to our supplier.
Important Note: It is important that the settings of the customer are done correctly, as well as ensuring they have both shipping and a billing address, otherwise our system will reject it.