Here's how:

1. Log in to your Shopify admin panel.
2. Click Settings.
3. Click Payments.
4. Select PayPal Express Checkout within the PayPal module.
5. Click Activate.
6. Once directed to a PayPal login page, log in to your PayPal account and click I Give Permission.
7. Click Back to Shopify.
8. Under Payment Authorization, select:
   • Automatically capture payments for orders (Immediate Sale).
   • Manually capture payment for orders (Authorize only).
9. Click Save.

Note: You'll find complete information and steps on integrating PayPal with your Shopify cart in Shopify's online manual.

While reactivating, select PayPal Express from the PayPal payment options.



See also:
Shopify Support