How do i change the footer?

The wp_footer() function is a WordPress hook. It allows plugins to place additional content at the bottom of the page – this is very useful if you’re installing tracking scripts like Google Analytics.

But that function is not what is adding copyright information or other junk usually bundled with free themes.

Instead, look in the theme’s functions.php file. There’s likely a function somewhere in there that’s outputting the content you see. You’ll also see somewhere this line:

add_action( 'wp_footer', 'some-function-name' );

That line will fire the some-function-name() function whenever WordPress calls wp_footer(). Just delete that line and you should clean your footer up.