I soldered one wire to the red wire at the battery compartment because there was enough room and the other on the PCB card where the black wire from the battery compartment attached. Once you have that done you just have to connect the other end to your adapter. This is where I used my "M" connector. It is important to match the polarities coming from the adapter to the proper wire connecting to your battery compartment. The controller's PCB were clearly marked which wire was the "+" and which one was the "-". If you get it backwards you will most likely damage the controller. After you've decided on how to connect the adapter just close up the controller and plug it in. You should be good to go!
WARNING: DO NOT HAVE BATTERIES INSTALLED IN THE CONTROLLER AND PLUG IT IN TO THE WALL AT THE SAME TIME!!!
Eventually I would like to figure out how I could have the batteries installed and just plug it in to charge the helicopter. Perhaps a small power select switch would do the trick?