Simulating an assembly in SimMechanics 2nd Generation

Hi,

I have successfully translated an assembly from Pro-E to SimMechanics ( 2nd Generation ). Its quite a huge component with several parts assembled together. So now each part has its own reference frame and connected to the world frame individually through a connecting port. Everything is clear till this point.

My question is how do i link two components together, I mean if i want to rotate a part with respect to the other part? Or is it easy if I use 1st generation??

Thanks a Lot!!

Best, Vish.