First you need to create a controller that will serve the data you want to show on the website
After that you have to create your component as explained https://www.odoo.com/documentation/15.0/developer/reference/frontend/owl_components.html
Inside this component, you will fetch the data from the controller and return them to the state

You can find a fully working example here in the module bookstore_portal I did when I was learning OWL, I just updated it to v15 and hope it will help you

https://github.com/peef-dev/appoo