Using OpenERP 7

I have created a private dicussion group and invited a client.

The client receives the invitation mail and can access to the group clicking on the invitation link.

But when the client logins directly in OpenERP there is no menu to access to that group.

If I create a sub-menu inside About us, the link is shown to all clients, not only the invited.

How can I show the link only to the suscribed client?