How do I make random spawn of enemies?

I want to do something like plaform game and i want enemies spawn randomly....

but i can't

Which part are you stuck on ? Do you have the basic platform working and it's only the spawning part that is the problem ? Have you gone through the tutorials ? Have you looked at the FAQs or tried the search for examples of this ?

is an example from a couple of days ago - uses families which are not in free version (are you using free?)