Account admins manage the users of a company account under Settings. Click your company name at the top of the sidebar and choose Users and Roles, or Invite people to go straight to the invite form.
The company menu at the top of the sidebar
The Users tab lists everyone on the account with their role, whether 2FA is on, and whether the user is active. Use the filter to search by user, role or last activity.
The Users tab
The Invite Users dialog
Invitations that haven’t been accepted yet are listed under Pending Invites, with when they were sent and when they expire. Click Resend to send an invitation again, or Revoke to cancel it.
Editing a user
In the same dialog:
There are three roles. Each one can do everything the roles to its left can do.
Anyone can reset their own password from the login page. Account admins can turn on two-factor authentication for their own login from Users; other roles set it up when they log in, if your account requires it.