Do you mean a piano roll? If you double-click any recorded MIDI item, it'll bring up the piano roll. If I want to enter something from scratch, I'll record a few seconds of dummy MIDI just to have an item to double-click.
Also you can select what style of MIDI note you see. You can choose lines for piano-type notes, or diamonds/points for drum-type data where you don't want to see the note duration.