If you mean attaching it to the AM tough box, It is not a simple task. If you are planning on using 1 CIM motor and 1 FP you need a additional gearbox to change its output.
AndyMark makes a good one.. You must use an adapter to change the output RPM's of the FP. You cannot just bolt on the FP.
If you mean attaching it to the black plastic gearbox, there are holes for mounting screws on the input end (The hole. not the white ring). I believe they are 4-40 screws. to mount it you simple have to put the screw through and screw the motor in.