We don't have a call to assistance button in Arbor. You would need to use an alternate method of alerting the staff member, such as sending a communication to the member of staff, or request assistance outside of Arbor.
Although there is no way to call someone directly in Arbor, you can add an Ad Hoc Intervention for a student. This will create a calendar event for the student and for the member of staff added to the Intervention. You can see how to set these up and use them here: Ad Hoc Interventions