Assigning a block H4 or H5

To have an H4 or H5, you need to set styles in CSS (size, font, weight, etc) and then use a code block instead of a text block and then use HTML to add your H4 heading text:

CSS:

h4 {
  font-family:Times New Roman;
  font-size:2rem;
  font-weight:600;
}
h5 {
  font-family:Times New Roman;
  font-size:1.6rem;
  font-weight:400;
}

HTML code block:

<h4>
  This is a heading 4
</h4>
<h5>
  This is a heading 5!
</h5>