Is there any quick way to do so from the administrator's account.??
Enable them via Administration > Site administration > Plugins > Message outputs > Mobile Notifications and see https://docs.moodle.org/33/en/Mobile_app_notifications for further details
Secondly, your users will need to log in via their mobile app to be able to receive the mobile notifications.
You can also set the default message outputs using the following page instructions
https://docs.moodle.org/33/en/Messaging_settings#Default_message_outputs