New to Java

I am running netbeans and have no problem compiling, and running in the netbeans environment.
When I try to do a "clean and build" and run the jar I receive this error: "Failed to load Main-Class manifest attribute from.. SRAG.jar" when running the jar.

I believe this is because I do not have a Manifest File.
Could someone explain how to create a Manifest File, how to use it, and if this is the error.

Thanks.