You’ll want to create a new firebase project, install the firebase CLI on your computer and then use the CLI to: login to firebase, select the project you created, and then using the CLI run firebase deploy wherever your code is. That should use firebase “hosting” to serve your static files.
I find Google Cloud’s documentation extremely confusing (including firebase), so you’re not alone on that front. Took a lot of searching & troubleshooting to finally get my setup working as I intended.