In order to accept payments, you must login to your PayPal account and enable Instant Payment Notification.

• Log-in to your PayPal Merchant Account and select the "My Account" tab
• Select the "Profile" sub-tab
• From the "Selling Preferences" options select "Instant Payment Notification Preferences".
• Click the "Edit IPN Settings" button.
• The "Notification URL" should be set to the fulldomain name of your website (ie http://www.mydomain.com) 
• Set the "IPN message" radio button to "Receive IPN messages (enabled)"
• Click 'Save' at the bottom of the page.

To ensure that your customers do not have to have their own PayPal account (ie you have the account, they just go and enter their credit card details at PayPal to pay you), do the following:

• Log-in to your PayPal Merchant Account and select the "My Account" tab
• Select the "Profile" sub-tab
• From the "Selling Preferences" options select "Website Payment Preferences".
• Ensure "PayPal Account Optional" is set to 'On'.
• Click 'Save' at the bottom of the page.