In order to run a procedure you will need to open a reference to the specific procedure, MainExecution in this case.

  IProcedure procedure = session.openProcedure("MainExecution");

Running a procedure that does not require arguments is quite straightforward:

  IProcedure procedure = session.openProcedure("MainExecution");
  procedure.run();

Close the procedure after usage:

  procedure.close();

The run method will block until AIMMS has finished execution of the specified procedure. Optionally, you can specify a timeout value as first argument. This value denotes the amount of time a procedure execution may take before an AM_Communication error is raised. 

The Procedure with arguments example shows you how to run procedures with one or more arguments.