You can insert a key at any time by pressing the "s" button. If you need to re-arrainge things, you probably should go to:
window>animation editors>graph editor. If you have not learned how to use the graph editor yet, now is a good time . . . You can find info on it in the Maya library. There may even be a training video for it somewhere, who knows.
"The Sage as an Astronomer: If you still see the stars as something above you, you lack the eye of knowledge." Friedrich Nietzsche