Think of a page as boxes stacked together. Common boxes:
<h1>Title</h1> — big heading<p>Paragraph text</p> — normal text<img src="URL" alt="" width="300"> — image<a href="https://...">A link</a> — link<ul><li>Item</li></ul> — list
Tip: Keep it simple. Add one thing at a time; hit Preview to see it.