Only Members can invite new users or approve Guests to join a room.
You can invite people on your team as Members to your workspace by clicking on your workspace name at the top of the left panel and selecting invite.
Then add their emails to the popup:
Workspace admins can approve/revoke Members and open up signups from a particular email domain (like @yourcompany.com) in the Workspace Settings page.
Inviting Limited Members
Limited Members can be invited from the room where you want them to have access.
First, click on the person icon in the right corner of the bottom toolbar. Then click on the Members tab. Next click " Or invite someone by email"
Now add in the emails of the Limited Members you would like to invite to this room and click "Send Invite":
The easiest way to invite a guest is by sending them link to the room. You can find the room link in the in the room's settings on the left side of the bottom toolbar: