on other types of carb with a similar type of choke
you just connect 12v to it when its needed
The earth is via the body of the carb
other bity's hopefully confirm this

Basically when it receives some electricity it slowly warms up and the warmer it gets the more it opens the choke. If the engine is already warm the residual engine heat is enough to keep it partially open so you arent starting with full choke.
You will get the idea and see if it is working by giving it 12V and observing as it magically opens the choke (unless its faulty of course)