Uploaded models are automatically stored in your profile when you're logged in. This way you can easily add them to your cart without needing to upload them again afterward. It saves time and comes in handy when you're dealing with large files.
For every model you order, a product page is automatically generated. So if you plan on adding an item to your shop, please note it should have been 3D printed before. Therefore, it makes sense to first order an uploaded model before trying to sell it. After all, our shop is a marketplace of 3D printed products.