To add PayPal as payment method to purchase in your shop you have to have a PayPal account. If you do so you just have to stick to the following steps:
Hit "payment methods > PayPal"
Choose the countries for which PayPal payment should be possible
Just enter Price if your customers have to pay an extra fee for this payment method
Enter your PayPal mail Adresse under "email"
Save and you're done :-)
+One of the most popular and fastest payment methods worldwide
Other payment methods under http://helpcenter.branchbob.com/branchbob-helpcenter-english/activating-payment-methods