As well as getting permission to use copyrighted material in a film, you may also need to get formal permission from people who participate in your film. This typically takes the format of a 'release form' which is similar to a contract, in which the participants agree to have their work used and distributed in certain ways.
Types of things you may need permission for:
There are many free resources online you can adapt to make your own documents, or check with your instructor if there are formal departmental documents you can use:
Pro Tip: A common practice in professional film making is to have participants sign the form, then read it while being recorded and looking at the camera.