What John is referring to is specifying the block itself. To me, this wasn't very intuitive since in BPM you must first define the block as a "Process". Then open the "Process" and select "Export Typ ...
I have also been able to successfully import models from Holosofx Workbench 4.2.2 into MW Runtime. What you may want to consider is importing the '.fdl' file that Workbench generates into M ...