Start a Group Call - Microsoft Teams for Mac
Microsoft Teams provides several ways to connect with multiple participants. Choose one of the following methods to start a group call or meeting.
Option 1: Add Participants to an Active Call
1. During a call, select People or Participants from the call controls.
2. In the Invite people box, enter a name, phone number, or email address.
3. Select the person from the search results.
Option 2: Start an Instant Meeting
1. Select Calendar from the Teams navigation pane.
2. Select Meet now.
3. Enter a meeting name if desired.
4. Click Start meeting.
5. Choose your audio settings.
6. Select Join now.
7. Click Add participants.
8. Add participants to the meeting or click Share invite. 
How to make a conference call - Microsoft Teams for Mac