Is it possible to import a FE Assembly to SIMPACK?

In ABAQUS, I have modelled a assembly containing two parts with lot of constraints and other engineering features which are very crucial to my FE analysis. The job ran successfully and I have got satisfactory results. As a next step, I would like to import this model into the Multi Body Software SIMPACK as a flexible body. This would require the introduction of substructuring concepts and I referred to SIMPACK tutorials for exact way of doing it. My question is, can we import an assembly into SIMPACK. Because the tutorials explain only a part being impoted into SIMPACK. SO when I follow the same procedure given in the tutorials to my model, ABAQUS gives me an error message saying SUBSTRUCTURE GENERATE cannot be used for assemblies. It seems it can only be used for parts. So how do I go about this?