How do I create circle around navigation arrow like this?

How do I create circle around navigation arrow like this in WordPress what's setting or code

I'm trying to add some CSS code at Custom CSS in WordPress but it's not working, and I'm looking for any setting for this, but I can't find out. This is what I can do.

All you really need is border-radius: 100% to make the button round. The icon at the can be horizontally and vertically centered with flexbox.

button {
  display: flex;
  font-size: 2em;
  color: white;
  width: 2.5em;
  height: 2.5em;
  justify-content: center;
  align-items: center;
  background-color: brown;
  border-radius: 100%;
  border: none;
}

<button>&lt</button>