As a cohost, you can start or join the webinar at any time. Cohosts can join the webinar sometime before going live to attendees, giving them time to prep in private along with the host and panelists.
RingCentral Webinar makes it simple for hosts to guide cohosts and panelists to join such a prep session up to 1 hour before the actual webinar.
You can click Join as cohost in the invitation just before the webinar. You can also copy and paste the link into a web browser to join.