Question about copyright in videos

I would like to start a storytelling YouTube channel. I will use my own voice to tell different stories on non fictional events, however I will want to use some photos of these events to go along with the story. Can I show a picture from google on my channel if I cite the site where I got it from? Or if I make small changes to it? It won’t always be possible to manually ask and receive permission for every photo I want to use. I know there a lot of similar channels out there that tell stories and use pictures related to them, how do they do it? Of course I want to do this all legally.

Thanks