How do I add SEO to my website? It’s not a thing, but there are, especially if you’ve got a WordPress website, there are some useful plugins like Yoast or RankMath.
Add those to your website and follow their very black-and-white recommendations that don’t take into account the subtleties of keyword research, backlink research, or a million of the other things that surround SEO.
But install those plugins and see how you get along.
I’m guessing the other interpretation of this question could be, ‘how do I add things to my website that might make it rank better from an SEO perspective’? That’s a topic far too long for this video, but if you’ve got a WordPress website, get RankMath or Yoast and connect your website to Google Search Console, and you will have added some facilities for SEO to your website in a very good way.
It’s a good start.