If you want some space around an element, give it a margin. That means, in this case, don't just give the <h1>
a bottom margin, but give <p>
a top margin.
Remember, when two elements are vertically adjacent and they don't have a border or padding between them, their margins collapse. That means that only the larger of the two margins is considered - they don't add together. So this:
h1, p { margin: 1em; }
<h1>...</h1>
<p>...</p>
...would result in a 1em space between the heading and the paragraph.