The Red and Black wire go to your AUX winding, which is the start winding of the motor. It is this winding that determines the rotational direction (depending on it's polarity) when the motor is started. This is the winding that has to go to the Drum Switch so you are able to change the motor's direction. Note, once the motor is running, the Drum Switch has no effect on changing the direction until the motor comes to a stop (no worries of slamming the motor into reverse while running). This is due the the centrifugal switch shown in your schematic. It switches out the start winding once the motor is up to speed.
To wire in the Drum Switch, you have to insert it into the wiring of the motor, what I outlined in my last post does that. This means taking off the existing Black and Red wires from their current terminals and adding additional wiring of the proper type and size for this application.
To start, disconnect both the Red and Black leads from their respective terminals as outlined and extend those wires to your Drum Switch. Then run additional wires from the motor terminals I outlined to the Drum Switch.
If you are not comfortable with and fully understand what is needed to be done, please ask for assistance from a motor shop and/or electrical technician. You need to hook this up properly, ground the system for safety, and use the proper gauge and type of wire for your equipment.