Thanks for reaching out to Jotform Support. I'm sorry you're having issues with your form. Are you referring to the appointment field? If so, can you please provide me with the link of your form?
It is really easy to enable these dates in your appointment field. Here's how:
In Form Builder, click the Gear Icon on the Appointment Field to open Appointment Properties.
Click Availability on the panel that opens on the right.
You may now set the availability of your appointment.