Zoom: How-to Invite a Participant to an "In-Progress" Meeting - Article

Please see below on how to add internal participants to in-progress meetings.

After you’ve started the meeting. 

1. Click Participants (drop up button) > Invite... OR simply click on Participants > Invite. 
   
   
   
                              OR
   
   
   
   
2. You will land in “Invite people to join meeting...” screen and select “Contacts”. 
   
   
   
   
3. You can choose the user that needs to be invited from the list or you can simply type to filter. 
   - Add multiple contacts to invite all necessary users at once. 
   
   
   
   
4. Once all attendees have been invited, select “Invite” and wait for the users to join.