I presume you are trying to compile the application and run it without using an IDE.
I also presume you have maven installed and correctly added maven to your environment variable.
To install and add maven to environment variable visit Install maven if you are under a proxy check out add proxy to maven
Navigate to the root of the project via command line and execute the command
mvn spring-boot:run
The CLI will run your application on the configured port and you can access it just like you would if you start the app in an IDE.
Note: This will work only if you have maven added to your pom.xml