Navigate to the patron add form through Patrons > New patron dropdown and choose any patron category from dropdown.
As it is possible to add or remove items from the Patron Registration form, the content may vary from site to site, however, it should look something like this:
All fields with a Required in red beside the box must be filled in before the record can be saved.
To designate a field as mandatory, the name of the field, as it appears in the borrowers table on the KOHA database, needs to be put into the system preference BorrowerMandatoryField.
For example, if a library wants to make emails a mandatory field, they would input email in the box of the BorrowerMandatoryField system preference. Each field inserted into the BorrowerMandatoryField system preference needs to be separated by a vertical bar.
After saving the edit to the system preference, Primary Email will have the word required in red beside the box and it will not be possible to save the record without entering a valid email in the patron form.
To find the borrowers table go to http://schema.koha-community.org/, look up the version of KOHA your system is on and find the borrowers table in the schema list.