Mandatory fields are useful when a key piece of data requires collection. It highlights to the user that the field must completed before they can save their work.
To set up Mandatory Custom fields, you will need to access the Control Panel
1. From the Admin panel select the entity you would like to set the field up against (i.e. contacts, objects or opportunities).
2. You can edit an existing field or set up a new field, simply switch the toggle to make the field mandatory.
3. Now, when editing or adding a new contact - the mandatory field will display with a star. The user will not be able to save their data until the field has been completed.