PayPal Checkout - Add Instructions for Customer Checkout

Have a non-profit client using opencart 1.5.1 and uses PayPal Payments Standard as checkout option as it is cost-effective.
A lot of their 'customers' do not have or use a PayPal account and have difficulty with checking out or do not know how to use PayPal checkout without creating an account. The client is wondering if there is a way they can add a screenshot or instructions to help with the PayPal checkout process.