To implement shopping cart in wordpress we can use Simple Paypal Shopping Cart plugin
To install a Simple Paypal Shopping Cart WordPress Plugin by the Search or Upload functionality
Go to plugins->Add New
Search Simple Paypal Shopping Cart plugin
The WordPress Shopping Cart is now installed successfully and now you can alter the settings for it and adjust the options according to your needs.
Go to Settings -> WP Shopping Cart and modify the various options.
Enter your Paypal email address to receive amounts for products you will create on your website.