Paypal is a gateway for accepting payments for purchases that can be used in PrestaShop.  In order to be used, the Paypal module must be installed and configured.  For more information on installing modules see How to Install Modules in PrestaShop 1.5.  The following article explains how to install the module in PrestaShop 1.5.

Installing the Paypal Module in PrestaShop 1.5

1. Login to PrestaShop as an Administrator
2. Bring your mouse pointer to the menu line and look for MODULES, you will MODULES listed again in a drop-down menu.  Click on MODULES and you will see the following:
   
   
   
   Scroll down until you find the Paypal module.  By default, it is already loaded, but NOT installed.  If you have Prestashop's Multistore option enabled, you will need to click on the checkbox if you have specified a shop.  This is shown in the screenshot above.
   
   


3. Click on the INSTALL button to setup the PayPal Module.  When installed you will see the following:
   
   
   
   
   
4. Click on CONFIGURE above in order to setup the gateway.  Here's what you will see for the configuration:
   
   
   
   
   You will need to have a Paypal account in order to proceed.  Otherwise, you can sign up for one.  Determine the options that work best for your business, then proceed to step 3 in order to save your configurations for Paypal and make it available for your customers.
   
   
   
   

After the configuration of the Paypal module is complete, you will be able to see the option available for customer to choose it as a method of payment.  It will appear in the checkout portion of the storefront such as below: