Below are some free online options for finding reusable media.
As a student, all sources must be credited in your work - even if they're public domain or CC0 licensed.
Try the Intellectual Property database to look up an artist before you use their work commercially: https://wiki.gettyimages.com/
YouTube's audio library for creators.
Royalty free music from Bensound. Licensing information: https://www.bensound.com/licensing
Audio Library is a channel dedicated to search, catalog, sort and publish No Copyright Music, Vlog Music and Royalty Free Music for content creators.