"Custom Fields" tab can be found under the settings page as follows :
All the existing custom fields are displayed here.
To create a new one, click on the "Create" icon as shown.
Fields Belong to : Select on which page you want your custom field to be displayed eg : Proposal.
Fields Order : Order of the fields in integer.
Field Type : you can select which field type you want to add to your pages eg : Datepicker, checkbox or Text box.
Toggle : If toggle to "Only admin" only the admin will be able to use , If the toggle is off the custom field is accessed by all staff.
Click on "Create" button.
NOTE: Activate the toggle button if the field should only be shown to the admin.
All custom fields are for the staff use only. They are not displayed to the customers.