Notes

So, you know how at the top of the page, there are different types of notes that you can click and then you are able to place that kind of note. (example: If you clicked on the quarter note, you would then be able to place a quarter note on the staff) Anyway, that option to click on the note is gone. The grid of notes aren't even there any more. I would just like to know how to get them back. Thanks!
-Tony McCahill