When you create the webinar you can specify people to be panelists. They will be sent an email message with a special link that will allow them to join the webinar as a panelist.
Each of them will have a different panelist Join Link. When they join the webinar, they will be listed in the Staff list, and they will join the webinar with their microphone turned on.
I do not do it that way, as I have had panelists accidently share their Join Link with others, which means that multiple Attendees will join the webinar with the Panelist's name and with the Panelist's special powers.
What I do is have all of my presenters join as a regular Attendee. When they join the webinar, I promote them to be a Panelist.
