How to Remove Powered By… from footer and insert copyright and year notice

Yesterday, I created the child theme. under the expound-child folder. I only have style.css file. I am trying to put copyrights on the footer. I have searched a lot of info regarding how to do put copyrights on the footer. Some said edit from footer.php and some said edit from funtions.php. Wondering if someone can tell me what’s the different between footer.php and funtions.php. According to the discussion above. Should i make new funtions.php like I did on style.css? Copy the code below and paste to the new notepad and save the file name funtions.php after that upload the file to child theme folder. Will i still see Proudly powered by WordPress…?

<?php
add_filter( ‘expound_credits_text’, ‘my_credits_text’ );
function my_credits_text( $text ) {
return ‘? ‘ . date( ‘Y’ ) . ‘St. John the Baptist Catholic Church’;
}

?>

Thank you in advance!