In this form, you can control which user/s should receive an alarm from one or more/machines. Select the user in the drop-down menu for the user. Move the machines from the left to the right with the arrows in the middle. The machines to the right will be the ones who the user/s will receive alarms from. Confirm the selection with the update button.
Changes done in this form will be saved/logged via "Client" -> "Left side menu" -> "Alarms". Here there is more information on how that form works.