It’s easy to do side navigation with flexbox.
It is enough to make a block with the nav class a flex container and distribute the elements in it with a bell.
Another thing to add is a width, say 150px.
For the body element, give a margin of 0px.

This task is part of the Full-Stack JavaScript Course.
If you have any issues with it, you can ask for community help below the post.
Feel free to help others if you’ve already solved the task.

index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Side navigation</title>
  </head>
  <body>
    <div class="nav">
      <a href="https://js.coderslang.com/navigation/217" class="nav-item">
        JS Coderslang
      </a>
      <a href="https://play.google.com/store/apps/details?id=com.coderslang.com&hl=en&gl=US" class="nav-item">
        Android App
      </a>
      <a href="https://apps.apple.com/us/app/coderslang-learn-programming/id1489105103" class="nav-item">
        iOs App
      </a>
    </div>
  </body>
</html>