itch.io

Here's a written tutorial that will explain all the windows and the basics: https://www.raywenderlich.com/7514-introduction-to-unity-getting-started-part-1-...

And here's a YT one :

The first 5m introduce the windows and then you could open the flatgame template scene and play around. And then optionally if you like watch up to minute 20, and follow along to understand how all the concepts fit together. The rest of the video wouldn't be relevant for you yet or for a flatgame at all really.