This project can be used as a starting point to create your own Vaadin application. It has the necessary dependencies and files to help you get started.
The best way to use it is via vaadin.com/start - you can get only the necessary parts and choose the package naming you want to use. There is also a getting started tutorial based on this project.
To access it directly from github, clone the repository and import the project to the IDE of your choice as a Maven project. You need to have Java 8 or 11 installed.
Run using mvn package && java -jar target/vaadin-app.jar and open http://localhost:8080 in the browser.
If you want to run your app locally in the production mode, run mvn package && java -jar target/vaadin-app.jar.
For a full Vaadin application example, there are more choices available also from vaadin.com/start page.