Basically, the helicopters can be considered little robots that will do the job you should otherwise perform, without any cost of energy: this means that you can have the CityVille helicopters collect your goods without spending energy!
This feature is only available to players who are at least level 30 in the game, who will receive a Helicopter Pad to place in your city. There are three different Helicopter Pads in the game and you will receive them via in-game quests.
So, once you will reach level 30, you will get the We Have Lift Off! mission in CityVille:
In order to complete the Helicopter Pads, you will need to ask for different parts from your friends. Here are the requirements for the Blue Helicopter Pad:
Now, after you have this done, you will be able to actually send the CityVille helicopters perform all the work for you. In order to do it, all you have to do is to click the helicopter and select which one you want to send – after that, a building will be highlighted and you will be able to send the helicopter there to collect form the building.