How do I add a standard price to a product in Lightning? Ultimately, I just want to associate products with my opportunities. 

From what I've gathered, you need to create a product then add it to the standard price book to get the option to add a price...but I need to add the standard price before I can add my product to the standard price book (or any other). The trailhead module was not helpful as it assumed previous entry of new products with prices and is dated 2017 with changes to standard price options impacting later versions of Salesforce Lightning.