You're using a preview version of SharePoint Syntex. Here you can learn how to create document understanding models by adding example files, training classifiers, and training extractors.
You can also import a sample model by going to the Models tab. The sample model includes sample files and a trained classifier that you can modify to learn more about how models in Syntex work.
Important: You'll need a license for the full version of SharePoint Syntex to apply your models to document libraries.
Learn how to get SharePoint Syntex here.