This builds on w3school's crash course. Use what you need.
First Page example (needs photo, uses local w3.css for stylesheet).
Then add an external styleheet and specify teal as the color for your div:
<div class="w3-container w3-center w3-teal">
From here on, inspect the page to see the code.
w3-third here to get a responsive effect.
Example (photos missing. But note these are specified as 100% each)
Uses the classes
w3-center for the text container and
w3-xlarge for the text in the code
Light-gray for div