I have an Airtronics VG6000. I know how to do this for my radio, but am unsure if the VG600 works the same way. Johan Nl brings up a point. Generally there are 2 ways to do this. Plugging one servo into the Aileron receiver slot and one into flaps and mixing flaperons with the mixing options on the transmitter. The other is using a Y-connector. Plug both servos into the Y-connector and then the single leg of the Y-connector into the receiver's aileron slot.

Didn't the radio come with a manual? If not, ask the guy you bought the radio from to find it and give it to you. If it came with a manual, all this would be in there.