The invitation can be done under the Home tab for each share. Manage will let you delete a user, pending invite or a shared link. Kindly check this documentation and hopefully it helps.
Brian is correct, the "Invite User" has been moved under the "Home" tab. It is the same button of "Permissions" in the kb link you had rollinga, but it has been renamed to "Share".
There was an issue in the previous method where the invited users would have access to all of the shares, so the newer method you would have the control on what data you are sharing to whom you invite.
