Hi,
You are running the Sierra operating system and unfortunately iMovie 9 is not entirely compatible with that system. Many misbehaviors have been reported. It is just not suitable to use any more. Also, iMovie 9 is no longer sold or supported by Apple. Since you are not very familiar with the program anyway, this is a good opportunity to upgrade to current version iMovie 10.1.6. If you are using the same Apple ID you used when you purchased your computer, you should be able to go to the app store to upgrade to current version iMovie.
Once you get iMovie 10 installed, here is a good online tutorial that will show you how to use its features.
http://help.apple.com/imovie/mac/10.1/
You want to use the Ken Burns feature to zoom into your collage to isolate one photo, and then zoom out and zoom in again on the next photo. I am not familiar with the .psd format that you mentioned, so not certain that it is compatible with iMovie. You'll need to try it to find out. The above help menu link will show you how to add music as well.
Have fun.
-- Rich