Schedule Sessions
This article describes how to access Blackboard Collaborate Ultra in your Blackboard modules, and use either the main course room or scheduled sessions for your live online classes:
Use the Course Room
The course room is an open session dedicated to your course (and is open 24/7). It provides you and your students a convenient session for live online classes or impromptu meetings. You simply click on the room to access it and launch a session.
Go to Virtual Classroom> Course Room

You can also edit the settings of the room:

Specifically, if you have a large class you may wish to deselect the option for participants to share audio and video:

If you forget to do this, you can also adjust this setting within the room during the live session:

Create a session
You may prefer to schedule a session to be open only for a particular day and time. There are a number of reasons you may want to create scheduled sessions over using the course room. For example, you may wish to create a guest link that you are sending to an external cohort for a specific lecture, or you may have a live session that will have greater than 250 attendees.
To do so, simply click the "Create Session" button, and adjust your settings according to your needs.
If you are using Blackboard Collaborate with a large class (greater than 250 students), you can also specify that it is a large scale session:

If you wish to know more about large scale sessions see https://help.blackboard.com/Collaborate/Ultra/Moderator/Schedule_Sessions/Session_Settings#webinar
See more on Session best practices