code for back to top

Look in your theme’s footer.php– https://<yoursite>/wp-content/<yourtheme>/footer.php. That is where you add your link. Put something like <a href="#top-link">Back to top</a>. Then, in your header.php you need to put a named link that matches– <a name="top-link"></a>. You could also just add the name="top-link" part to some other already existing link that happens to be near the top.