Hi Renascence-
You can customize your footer without coding a new file in the Customize > Advanced > Footer Settings. There you’ll be able to modify the contact details, change the attribution links, and add custom widgets to include any content you’d like in your footer.
If you would like to custom-code a new footer, you should do it by creating a child theme, where you’ll be able to override the template from your current theme by creating a file called footer.php in your theme’s templates/footer/ directory.