Simply add name and email as a minimum. Further details can be filled in thereafter. Use as an address book and for quick referral, contacts may be labelled and have reference notes.
As a minimum, add the name of your contact.
To make more functional, add the contact's email address. The email address is needed for Event Invitations, should you wish to use that feature.
The contacts table can show all details per row.
Contacts can be imported & exported via CSV from the via the "Table" view.