If you plan to have PayPal as a payment method in your store, your PayPal account needs to be active and configured through the API programmer interface.
You can find out exactly how to do that in this article.
To add PayPal payments to your store:
1. Click on Settings > Payments and click Enable next to PayPal’s logo:
2. Fill out the form with the information acquired from PayPal. Remember that the username and password are not the same as your login and password to your account.
3. Pay attention to connect your payment method with selected delivery methods. To do this click on checkboxes on the bottom of the page:
4. Save the changes and you are ready to go!