Are you using a WordPress theme where there isn't an option to change the footer copyright credits?
Personally, I find it tacky when a theme developer makes this so hard to change.
But you are in luck, all WordPress themes and plugins are GPL licensed. This means you are freely allowed to change the code, you can even resell it as your own.
So in this video, I show you the easiest way to change the footer copyright credits in any WordPress theme.