Adding custom cursor from codepen

Try adding this to Home > Settings > Advanced > Code Injection > Header

<style>
  body .cursor {
  pointer-events: none;
}
body .cursor__ball {
  position: fixed;
  top: 0;
  left: 0;
  mix-blend-mode: difference;
  z-index: 1000;
}
body .cursor__ball circle {
  fill: #f7f8fa;
}
</style>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/1.20.3/TweenMax.min.js"></script>
<script>
  const $bigBall = document.querySelector('.cursor__ball--big');
const $smallBall = document.querySelector('.cursor__ball--small');
const $hoverables = document.querySelectorAll('.hoverable');

// Listeners
document.body.addEventListener('mousemove', onMouseMove);
for (let i = 0; i < $hoverables.length; i++) {if (window.CP.shouldStopExecution(0)) break;
  $hoverables[i].addEventListener('mouseenter', onMouseHover);
  $hoverables[i].addEventListener('mouseleave', onMouseHoverOut);
}

// Move the cursor
window.CP.exitedLoop(0);function onMouseMove(e) {
  TweenMax.to($bigBall, .4, {
    x: e.pageX - 15,
    y: e.pageY - 15 });

  TweenMax.to($smallBall, .1, {
    x: e.pageX - 5,
    y: e.pageY - 7 });

}

// Hover an element
function onMouseHover() {
  TweenMax.to($bigBall, .3, {
    scale: 4 });

}
function onMouseHoverOut() {
  TweenMax.to($bigBall, .3, {
    scale: 1 });

}
</script>

Hey, it's not working @tuanphan