In simple terms, your method only takes 3 parameters, and one is an output dataset, so only 2 input parameters.
To learn how parameters are used I find it best to locate the method in a BPM widget so that I can see what is required. In this case, the method StartActivityByEmp takes 2 input parameters, and one output parameter. See the screenshot or navigate to the method in Labor.StartActivityByEmp.
StartType is either P for production or S for setup.
In order to add the other fields you need to record a labor entry (job, assembly, and operation), you have to see the other methods that epicor uses. Run a trace, then perform a manual start production activity.
Use Jose’s trace parser to find the methods used. Trace Helper Utility for Epicor ERP 10 - Epicor ERP 10 - Epicor User Help Forum. Or use the kinetic version if you want: Kinetic Trace Helper Utility 1.0 (Kinetic Web) Chrome Extension - Kinetic ERP - Epicor User Help Forum
The last time I checked, these are the methods that get triggered when an employee enters time on the MES.
I think you need at least StartActivity, DefaultJobNum, and DefaultOprSeq. But in reality, you may need more of these methods to fully replicate a proper labor entry.
Good luck!
Nate