If the product was ever purchased (even once, or by the Test order), you cannot delete it:
When a customer purchases a product (or, when you run a Test purchase), a corresponding data record appears in the database. This record cannot be deleted later.
However, you can remove a product from the marketplace by deactivating it. To do that, go to the Product Edit page and switch the toggle button to inactive state:
Customers and Affiliates do not see a disabled product. It is impossible to purchase or promote a disabled product.
If nobody has ever purchased your product and you haven't run a test order with it, you can delete a product. For example, you can delete a freshly created product if you have mistakenly set the wrong Product type: