If you want to use PayPal as payment method on your store you will need to enable Express checkout on your PayPal account first.
STEP 1. Go to your Seller preferences
Login to your PayPal account and then click on Seller preferences.
STEP 2. API access
Search for the API access option and click on Change.
STEP 3. Enable Express checkout
Scroll down until you find the link Enable Express Checkout and click on it.
STEP 4. Accept PayPal payments from your online store
Make sure the first option is selected: Accept PayPal payments before API permissions or credentials are set up.
Click on the Submit button and you are done. You can now add your PayPal email to your store as a payment method.