It is incredibly important that you cite your sources for any audio or visual resources that you use. You should also give credit to your actors, videographers, editors, and any guest appearances.
An easy way to think about giving credit in your video is to use the TASL acronym, which is Title, Author, Source, License.
"Creative Commons 10th Birthday Celebration San Francisco" by tvol via Twitter is licensed under CC BY 2.0
"Big Horns Intro" by Audionautix via YouTube Audio Library is licensed under a Creative Commons Attribution license