There are a few ways to reference a PlayMakerFsm in your scripts:
1. Add a public PlayMakerFSM variable and link to the component.
2. Use GetComponent to get an PlayMakerFSM Component on a GameObject.
3. Use GetComponents and the FsmName property to find a specific FSM on a GameObject that has multiple FSMs
Get all PlayMakerFSM components on a GameObject using GetComponents<PlayMakerFSM>(), then loop through them and find the one with the right FsmName.
EDIT: There is now a static utility method in PlayMakerFSM to make this easier: