Happy to...
In this example I'm adding Playmaker Actions to the particle system itself. But that's not necessary. The way this is set up, pressing space will toggle the particles emitting on/off. That's what the Bool is for, unticked is off, ticked is on.
The first picture highlights the component label you have to drag and drop on to the Set Property part you see in the last image where it says Particle System. Then you get the options specific to it.
Hopefully the pictures can explain it. Let me know if you need more info.
There's a quirk where if you want to assign a component from one object to a Playmaker FSM assigned to another, you have to turn on Lock so you don't deselect it in the process. This is why for this example I put the FSM on the Particle System itself.