Stanford Encyclopedia provides a pretty straightforward interpretation: "Malebranche is known for his occasionalism, that is, his doctrine that God is the only causal agent, and that creatures merely provide the “occasion” for divine action."
In other words, my understanding is that God is The only cause... therefore, people are merely effects of God. Thus, people cannot be causes, they are simply the occasional effects of Gods intervention.
Does this make sense? What is your understanding?
Also - in terms of our body and mind, Malbranche thinks that they are both subject to the intervention of God.
-pk