You can use one payment option, such as PayPal, on your order form, or you can use two or more payment options. Each payment option will need to be set up separately under Settings > Payment Integration.
When using multiple payment options on a form, you will need use Smart Routing on your Submit Actions.
For example, say you wanted to offer all four current payment options on a single form. One way to do this would be to create a select list on your form called “Choose a payment method” with four choices: PayPal, Google Checkout, Authorize.Net and First Data.
For your smart routing rules, you would set the PayPal Submit Action to redirect the user to PayPal if they pick PayPal from the “Payment method” select list, you would edit the Google Checkout Submit Action to redirect them to Google Checkout if they chose that option from the select list, and you would do the same for the other two payment options. You set this up under Settings > E-mail & Redirects > After the Form is Submitted.