How do you have someone declared persona non grata?

It is a Latin term that literally means that a "person is not welcome" and it is used when one nation officially notifies another nation that one of their citizens is barred from ever entering their counry.

Individuals cannot, technically, apply THAT term, but you can 'bar' someone whom you do not want on your property by having a "trespass warning" or a "barring notice" issued to them.