Note, this app can only be used on Shopify Plus stores that support checkout extensions. If your store still uses checkout.liquid to customize checkout, please upgrade to the new checkout before proceeding.
From the Shopify admin page, navigate to Settings > Checkout.
Click the Customize button next to your live checkout profile.
Click Add app block at the bottom of the Delivery section in the sidebar.
Click on the ZIP Lock app block.
Under Checkout behavior check "Allow app to block checkout" and "Include app in Shop pay".
Click Save in the upper right hand corner of the page.