Note: Not registered with UPS yet or do not know your developer credentials? Simply follow this quick guide from Shopify.
Adding your UPS credentials to Store Pickup + Delivery
Open Store Pickup + Delivery, head to the Rates Page, scroll down the page to the Shipping section and then select the Advanced Options
From the pop up modal select UPS
Check Enable UPS rates and enter your Username, Password, Account Number and API Key.
Once entered simply Save and your UPS rates will be active via the shipping channel of the app!