Those are the modern European colors of brown=hot, blue=neutral and as always green=ground... Europe puts a yellow stripe on it.
All of these converge onto a 3-row terminal block, which is the usual method of interconnect in Europe. Note that all the wires to that terminal block enter the same side. That tells me the other side is intended for the external power connection. That's where you hook it up. There are screws to clamp the wire, looks like the screws are on the other side.
I assume the unit is meant to be permanently installed and hardwired. If you put a flexible cord-and-plug on it, make sure to have proper strain relief on the cord - preferably into a metal hole. The mounting area there is plastic and you could damage it with a hard yank on a cord.
The receptacle on the white part has nothing to do with supplying power to the unit. Once it is hooked up, this is a convenience outlet for small appliances, and appears to be the CEE 7/5 type common in Czech Republic, Austria and France. The ground may not work with other styles of Euro plugs, and you may be able to change the receptacle to a type more convenient to you.