Before a meeting
To invite someone to join a meeting, use the Invite people box to search for and invite people when you schedule or edit a meeting. Then, you can use the scheduling assistant to see times when everyone is free.
In a meeting
When you're in a meeting, select Show participants in your meeting controls to see the people who were invited but haven't joined yet.
To ask someone who was invited to join the meeting, select their name > More options > Ask to join
.
You can also type a person's name or phone number in the search box to add someone who was not previously invited.