I drew up a couple of schematics that should help.
First one for the motor driver with direction control.
Second one for a view of the switch wiring(rear view)
Third is the pinout for the Transistor#
Any DPDT* switch will do, be it slider or toggle or rotary.
Note that the base resistor(1k5) in the motor driver circuit is for a 5v supply.
If you run the logic on the same 12v supply as the motor, use a 3k3 resistor.
#The transistor marking(part code) is facing
away from you in this view - Metal tab is facing you.
*(Double Pole - Double Throw)
Edit, a pinout for the transistor will help
