You will need to update Zoom to version 4.6.10 or higher to see the following security features.  You will now see a Security tab next to Participants when you are hosting a meeting.

Security tab you can change the following setting while you are hosting the meeting.

1. Lock Meeting. If the Lock Meeting is checked it means that no new participants can join the meeting.

2. Enable Waiting Room. This will make it so that any participant that wants to join the meeting has to be allowed by the host.

3. Share Screen. If this is checked off then your participants will be allowed to share their screen with everyone at the meeting.

4. Chat. If this is checked off, participants will be able to post on the chat or send messages to each other while the meeting is happening.

5. Rename Themselves. If this is checked off the participants will be able to change their Zoom screen name at any time during the meeting.