How to add custom css to a square website

square-website-builder-custom-css.js

<script>
var parentWindow = window.parent;
// Create our stylesheet
var style = parentWindow.document.createElement('style');

style.innerHTML = `#YOUR_SELECTOR_HERE {max-width: 100% !important; padding: 0; overflow: hidden; }`;

// Get the first script tag
var ref = parentWindow.document.querySelector('script');

// Insert our new styles before the first script tag
ref.parentNode.insertBefore(style, ref);

</script>