Just like this:
One fan is blowing, one fan is sucking. I did this because the freezer kept "freezing" up and would need to be defrosted. So my temp probe is actually in the fridge and is set to the temp I want to serve my beer at. But the temp is usually pretty close in both the fridge and the freezer. And the freezer no longer freezes up since it never gets below freezing in there. I started off with just one fan, blowing from the freezer in to the fridge but it felt like the fan wasn't pushing much air when the freezer door was closed so I added the second fan to help get better air flow. I'm using the eBay temp controller that's popular on the forum but I only have the "cold" side hooked up since I never need it to get warm. The fridge is controlled by it but the fans run all the time.