Crediting for Mods and Caws

[jimmyacon]

Hi all

I'm a bit new to this and wanted to make sure I do it properly. I'm planning to start broadcasting my Universe on YouTube, but I have a large number of downloaded CAWs and mods for characters. What's the deal with using other people's CAWs in my own YouTube videos? Do I need to go back and figure out which user created them and try to contact them in advance for permission? 

Thanks

Jimmy