How do I add another tab to the group menu and show its content

I am trying to add a new tab to each group and haven't really been successful so far.

I tried to use the information provided at

I added this to the function.php - but it didnt really change anything...

I would really appreciate a working sample, that I can use for bp 1.7. I searched around the web and this forum but couldn't find an easy to apply answer ...

Thank you for your help