i try to explain, however sorry for my poor english.
first you have to open the spektrum module. take off the antenna from the casing then take off the cable that attached to the spektrum board.
next open your m11, take off your old antenna and the silver thing on the bottom of the antenna. grind the antenna slot so it will fit the spektrum antenna.
drill a hole in the back of the m11 cover, slide the cable then attach the cable back to the spektrum board through the gap in the spektrum module casing.
oh btw there is a step by step guide available on the internet, just google it.