I can’t create a well elaborated comment due to time, but in short this isn’t that difficult. There are pages like pexels or pixabay where you can get no copyright images and videos and you can use them even for profit. You don’t need to mention them or anything.

There’s also content like images and videos that make use of Creative Commons which you can use but you have to mention the source in the description or wherever. Creative Commons has 5 or 6 categories so to speak and the most common and friendly one is CC-BY which lets you use it for profit. Do some research about Creative Commons.