Hello! How can I add something to the form to allow someone to order mo

For this type of set up, I would suggest using regular fields to set up your options.  You can then assign calculation values to those options:

http://www.jotform.com/help/301-How-to-Assign-Calculation-Value

And perform further calculations:

https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form

You can then pass that total to the payment field:

https://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field

The following guide under the "Calculated amount based on user selections and inputs" has an example of how to do so:

https://www.jotform.com/help/323-Mastering-Payment-Form-Integrations-with-JotForm

This setup gives much more flexibility in setting up your options.