Introducing new ferret

Hi all,

I bought a new female ferret today so that my male will have a buddy. My male is about 4 - 5 months old, she is three months, they are both fixed. 
I have not introduced ferrets before and wanted to get an idea of how playful behavior should look.

They both run around and war dance while panting. They don't dook at all, it's a quick pant/"heh heh". As I understand it, this is just a kit thing? How can I tell if the female is not having fun/is afraid? 

Hobbes, my male, also lies on top of her. Is this an attempt at playing or is this a dominance thing? He doesn't really bite, just puts his whole body over her back. They seem to be doing fine but I want to be aware of negative behavior.

Thank you!

It sounds like they are playing, and that's what you wanted.  Even my older ferrets play rough.  If you see one grabbing the other and shaking, or poop or pee, it's getting serious.  Even then, we've had to let a couple pairs fight it out just to settle things.
Let em play and enjoy!

THE DOOKS OF HAZARD

Thank you very much for the reply! New ferret owner here haha, trying to learn all their different behaviors