You use a dual aileron plug. Both ailerons are controlled by the same channel. The plug/harness (I forget the technical term) plugs into the receiver and the other end has two sockets, one for each aileron servo and it makes them work opposite of each other.

In order to use "flaperons" you have to use two channels. On my radio its channel six. This way each servo can receive different signals so you will be able to lower both ailerons at the same time.