Accordions: Open first tab

To keep the first accordion or tab open, you can add this code:

/* Open first accordion */
.accordion-content {
  padding-left:1rem;
  &:first-of-type {
  display:block;
  }
}
/* end open first accordion */

Where do I add the code?

Use this link to learn where exactly to add this code snippet:

Where to add your CSS style code