To render the results of a MassFX simulation, or if you want to tweak aspects of the simulation manually, you need to bake the project. Baking creates standard keyframed animation for dynamic objects and converts them to kinematic objects.
To bake the entire scene, click Bake All on the of the MassFX Tools dialog. The simulation will run for each frame and store the results as keyframes, after which it converts all dynamic objects to kinematic.
If, after baking, you want to adjust the simulation, click Unbake All. All baked keyframes will be deleted and the objects returned to dynamic. Because MassFX keeps track of which objects were converted to kinematic due to baking and unbakes only those, it retains the status of objects that were kinematic to begin with.
You can also choose to bake or unbake only items that are selected in the scene. For example, you might want to use simulation to generate the path for a kinematic object, and then lock its motion to the simulated results before putting other dynamic objects in its path.