...can't get the plug to stay in the bottom of the oil filler thing.
not sure I need to care much....or do I...?

It keeps oil from splashing right up in the the Pcv/tube and in to the intake.

I've had a bunch of parts cars and all of them didn't have this plug....and the one that was fell out wont stay in the hole.
it doesn't look damaged, is there a "trick" to getting it to stay in???
the threads on the piece don't seem to be.....threading.....

You could just as easily clean and degrease the surface really well and use foil tape to block it off. Or check your local hardware store for rubber plugs and use one of those.

thanks....probably go with the rubber plug if I can't force the old one in.