Had to add a tab to a mySite Host.
Go to your mySite Host, Site Settings, Under look and feel there is a quick launch.
Add it there.
Depending on what you want to add, i created a new List and under the url added the url for the list...This will open in a new window.
To open the tab the same way the other tabs open (Keeping the user profile box) you need to use ASPMenu.
Have not done this but you will prob get a solution if you include ASPMenu in your search