In Motion, I have an image that is spinning and also dropping from the top of the screen straight down to the bottom (slowly). I want to stop it dropping for a few seconds and then continue dropping, all the while continuing to spin it. Is it possible to this perhaps with keyframes? If so, how do I add keyframes in Motion?
Yes, you'll be keyframing the Position parameters.
Section 5, "Keyframing"
There is a lot of options available in Motion for keyframing. You could even do it with a Throw behavior. Just make the first Throw behavoir only last for the first segment of the droping down. A second one for the second segment of the dropping down.
There is way more to it than could resonabley be covered in a forum post.