Make search bar work

So I have put a search bar here on this code pen:

And I wonder how I can make it work in a small site? For example if someone searches “cats” and there is a post about dogs somewhere on the site. How can I make that work so that people are sent there? To that post I mean.

Did you try searching and find something that you didn’t understand? If so, tell us.

I did a quick search and found some examples.
At a bare minimum you’ll need to use HTML, CSS and JavaScript.