How to run the main() method?!

[HowardHsiao]

Origin words:
[Execute the main() method of one of the demo applications, for example com.dataartisans.flink_demo.examples.TotalArrivalCount.scala. Running an application will start a local Flink instance in the JVM process of your IDE.]

I've follow steps / READ-ME.txt , but I still do not understand what's the words meaning. There is no able to execution of main() method in the project. ( I even use the IntelliJ-IDEA/Netbeans/Eclipse , 3 IDES to check up the codes.) I also installed scala for just testing a single file. I'm confused up. Could you please be kind of making the intros more clearly? Thanks!