Create a business PayPal account and connect to your Shopify store. Please check the Shopify official guide here. https://help.shopify.com/en/manual/payments/paypal/set-up-paypal
Julie here from Shopify Support.
It's also worth noting that the PayPal Express Checkout payment gateway is automatically activated with the email address you used when you first signed up with Shopify. You should be able to see this in Settings > Payments. While this would indicate that you are all set to accept PayPal payments, it's a good idea to ensure that you've completed the account setup on PayPal's end before you do so. This will ensure that you receive payouts from orders made with PayPal right away.
If you do not already have a PayPal Business account, then you can sign up for one here. Once you have a PayPal Business account, you can connect your account with Shopify by simply deactivating PayPal in Settings > Payments and reactivating it using the email address associated with your PayPal account. We also have instructions on how to finish setting up your PayPal account with Shopify here.
If you aren't seeing PayPal Express in your payment settings, then you may be located in a region where PayPal is not supported. If this is the case, then you can see which gateways you can use by selecting your country from our list of available payment gateways here.
I hope this helps guide you in the right direction! Let me know how that goes. Are you planning on using any other payment gateways aside from PayPal?