Hard to explain this without graphics , but i'll try . Probably best to take the bridge off . Mark the centre line of the hole that the tremolo drops into and transfer the mark to the side of the bridge , centre it on the side and pop a mark on it with a punch . Now , depending on how much room you have , you drill hole at 90 degrees into the tremelo hole , the hole size will depend in what size screw you are putting in , You can find , charts for tapping drill sizes on the net . Drill the hole . This is the delicate part , the tap is going to be pretty fine , so don't get heavy handed , if you break the tap in the hole , you are in trouble . Take the tap out and clean it , then run it back a couple of times to clear any shavings from the threads , Now , put the t/arm in the position you want and mark the centrline of the tapped hole on it , Grind , file or machine a flat spot a little wider than the screw diameter on the t/arm . Put the arm back in , put a socket head screw in the threaded hole , making sure that it is nor overtight , just firm . Taps are expensive , especially if only used once , if you don't have the gear , take it to a machine shop . It's a 15 minute job for them . Good luck