From a Teams channel, click the video camera icon to start a meeting. You do not need to have a webcam to do this - you can do voice-only meetings.
Choose 'meet now'. Add a subject if you like!
Anyone in your channel can join a meeting held in that channel. You can invite additional attendees directly in the 'People' sidebar on the right.
Most devices such as microphones, cameras, and speakers will set up automatically, but if you need to adjust a setting, you can choose the '...' menu and then 'show device settings'.
From a private or group chat, select the video camera or phone icon from the upper right corner. If you do not have a camera, that option will be grayed out.
The people you're trying to call will see a notification and will need to answer (or refuse) the call.
Start a video meeting by clicking the video camera icon.
Once in the meeting, choose the 'share screen' icon.
Choose which window or application you want to share with the video meeting.
Starting Chats and Calls in Teams
Creating Meetings in Teams
Joining Teams on Your Phone