Firstly i'm sorry i'm not able to show you exact process for paypal, because PayPal business accounts are not available in my country
Make sure you have Business account before using paypal
Log in to your PayPal Business account.
Click the My Account tab.
Click the Profile tab. If you haven't already done so, you need to verify your account before requesting API credentials.
Click Request API credentials under Account information.
Click Set up PayPal API credentials and permissions under Option 1.
Click Request API Credentials.
Click Request API signature.
Click Agree and Submit.
Copy and paste the API username, password, and signature into your shopping cart's configuration or administration screen.
Complete the process by following your shopping cart's final steps.
Open and edit
Provide your keys
PAYMENT_PROVIDER=paypal PAYPAL_USERNAME=yourPayPalBusinessEamil@something.com PAYPAL_PASSWORD=YourPassword PAYPAL_SIGNATURE=YourSignatrue
You are done.
Visit Admin Panel -> Currency/Charges to set currencty and charges