You'll need 2 holes... One in the side behind the lower section for air inlet AND access to the business section of the unit... Another one either in the side near the roof, or in the roof. Both holes have special covers that you can buy on ebay...
Covers for the side are THESE
The roof vent will look something like THIS
Remember, the RV style refride uses heat to make things cold (don't ask me to explain how it works), and it'll need adequate ventilation or it will not do it's job.