I would follow through the tutorials, even if they dont seem to be what you want. They teach you the foundations of how to use playmaker.
To generate random amounts of time, you can use the "random int" action, and save it to a int variable. Then use that variable in the "wait" action. 1 = 1 second.
I have a simple tutorial about actions/events/states:
There is a tutorial on udemy about FPS and playmaker, but I would still do the basic playmaker tutorials first, even they don't seem to apply. First few at least. Especially learning about states, events, actions and triggers.