It is a standalone WatchOS app. You do not require and iPhone app.

There is a document to walk you through the code so you can configure and customize it. To deploy it to your Apple Watch, you simply attach your iPhone to your Mac computer and use Xcode to deploy it to your watch. If you are asking about a submission to the Apple App Store, there is a guide Apple provides here: https://developer.apple.com/watchos/submit/

I am also available to support you through your process.