fill field

Were you looking on how to prepopulate the form fields?

You can achieve this using the Field Prepopulator app 

link: https://apps.jotform.com/app/field_prepopulator

OR

Using population via URL parameter value.

User guide: Prepopulating-Fields-to-Your-JotForm-via-URL-Parameters

In case you are looking instead for Autofill option, here is the user guide: How-to-Enable-Auto-Fill-Feature

Let us know if you need further assistance.