This is usually done be editing your theme’s footer.php file. If you can provide a link to your site, perhaps I can give you a more precise answer as to where to insert the copyright code.
Adjusting the size of the footer can probably be accomplished with an addition to your child theme’s style.css file. Once again, if you can provide me a link, I can give you the specific code to add.
I use the developer tools in Firefox (Ctrl+Shift+I) to inspect the code and then narrow down what elements are causing the issue. You can edit the css live in the browser to see what changes will do the trick.
I do this every day as my profession, so its second nature. I live and breathe WordPress. ??