Add measures using the 'Bars' window is usually pretty good way to go.

You click the 'E' for the 'event list' of a track and see every midi event, and edit any parameter for it.
You can use the notation window to edit notes also..
And lastly (a favorit with some) is the piano roll window.

You can edit, add in any of these places.
If you add bars, make sure you highlite all the tracks you are adding bars too.


I do not work here, but the benefits are still awesome
Make your sound your own!