There are a lot of sources that claim to provide copyright free music for free, but this is often misleading! I have had to re-do several videos after getting a copyright claim on youtube. This means that you can “use” the audio, but the copyright owner can run theirs ads on your video, and you have no control on how many or how long they are. You can test this ahead of time, add the song to a video, even if its blank, export it and upload to youtube as private, it will still be scanned and you will be notified if the song is claimed.
The better way is using a service like Epidemic Sound or Audio Blocks to obtain royalty free music and never have to worry about it. I have found a few creators who do allow you to use their music as long as it is credited in the description, like: Joakim Karud and FreeMusic109
The totally free library at YouTube is also a great resource, they have music and sound effects: YouTube Music Library for Creators