First, you need to get the ID of your to be embedded short video, this is what you can easily extract from the sharable URL from Youtube, for example

1550 x 959, 753.9 KB, PNG
Then, replace your video's id inside the below snippet, feel free to update the title as well.
html
<iframe width="315" height="560" src="https://www.youtube.com/embed/Your_Short_Video_ID_Here" title="Your Title" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen ></iframe>
You're all set!
For your information, the ratio of Youtube shorts is 9:16. So 315:560 is one of the nice dimensions for this ratio.

