Before diving into JCal Pro fields, it's worth checking this guide to JCal Pro forms.
We recommend starting with forms, because you need to create a form before you create fields. You need to understand whether to create an Event Form or a Registration Form.
The JCal Pro Fields admin page allows you to create, edit and keep track of your fields, which you can use in forms.
This next image shows the same screen with multiple fields. Click here to see the field types that you can use.
Each field is customizable with descriptions and default values. You can also have custom permissions for each field.