Hank here from Shopify!
First off, great work on getting not just your first, but your second order! That just shows how much work you have put into your store, and now it is time to acknowledge your effort!
Now in relation to your query about Oberlo, it is a bit of a different process than the way you described. First, the customer places the order on your store and pays you for this, then you would need to place the order for the product itself via Oberlo.
I will also share this guide with you, as it talks you through the steps needed to place your first order and is a great guide to save as a bookmark if you are ever unsure.
Let me know if you have any further questions, and great work getting your first order!
All the best, Hank.