How to Invite External Users
Schedule the meeting: Open Teams and navigate to the Calendar tab. Click New meeting.
Add emails: In the "Add required attendees" filed, type the external user's email address (Gmail, Yahoo, or other business accounts) and press Enter
Include Details: Fill in the title, time, and any meeting agenda or context in the description box
Send the invite: Click send. The guest will receive an email containing the direct "Click here to join the meeting" link
External User Requirements
When it is time for the meeting, the external user simply clicks the link in their email. External users can choose to continue in their web browser (no installation needed), download the desktop app, or sign in if they already have an account. They will need to type their name to be identified and may wait in the lobby until you admit them.
Additional Information
Teams Meetings - External Access