How do I put in a session fee box and a date box that I can fill out for the client?

I want to fill out the date, time, fee, tax for the client before sending. How do I do this

You already have the fields in the form so I think you sorted this out already. Do you want to calculate field values and pass it to the payment field? If so, you may consider checking the following guides:

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

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

If you have further questions, please let us know here.