How to clear dummy articles on news sites

Hi! I’m a total newbie setting up a news site with WordPress. I’m using a news site template.

I’ve watched YouTube tutorials and was just wondering how you get all the dummy stories off the site?

I watched an example with one guy publishing one story but then all the other dummy stories remained on the site with it.

Do you just have to flood your site with enough of your own content to flush the dummy articles away?