PayPal is very famous payment system used by over 267 million people world wide (statistics updated 1/1/2019). It is very easy to use and secure system to pay and accept payments. They also accept Credit Cards even if you don’t have an PayPal account.
You will first need to make sure that you have account in PayPal already registered and ready to accept payments.
Also don’t forget that before making any changes to your store, you should put it in “maintenance” mode and backup your store just in case something goes wrong.
Go to here and download the PayPal & Braintree official PrestaShop Module (choose module version corresponding to your PrestaShop version e.g 1.7) and save the zip file somewhere on your computer.
Now go to your store back office (Admin) and then on the left navigation screen. Go to “Modules” tab and click on the “Module manager”.
After the page finish loading, on the upper right corner you will find an “Upload module” button. Click on it and and choose your downloaded module zip file location from your computer.
Once the module is installed, click on the “Configure” button that will appear and you the screen below.
On the right box (the one with Credit Cards), click the “Activate” button. Enter your account credentials, and then to authorize PayPal to your store.
Once the authorization is complete, you are set and you can accept PayPal payments on your PrestaShop store.