Yes, all the volunteers must be created as V4S Mobile users. When a new volunteer is registered either from V4S Kiosk or V4S Personal, a record is automatically created for that volunteer as a V4S Mobile Users. You can also, upload lists of volunteers into the V4S Users table,

Volunteer Coordinators / Administrators that login to the V4S Kiosk app must be created as V4S Mobile Users with a field  "is Kiosk User" enabled, only then the V4S Kiosk user can log in to the V4S Kiosk application.