How can I use a telephone line in Blackboard Collaborate?

Blackboard Collaborate telephone line offers the following features:

• A telephone line is dedicated to each session with a maximum of 25 call-in users. (for more information see: https://help.blackboard.com/Collaborate/Ultra/Moderator/Get_Started/Call_Into_a_Session
• A direct link can be created to a Collaborate session which allows anonymous viewers to enter as guests (class presentation) or moderators (team collaboration) 
• A phone number can be shared in 3 ways: 
• before the session in the email invitation, 
• in the Blackboard course item, 
• during the session in the call-in menu.
• Sessions can be automatically dedicated to registered students with email invitations or through a Blackboard course workflow.