Does anyone know how to install a taxi meter in a 91 buick park ave?

i have a centrodyne 610 taxi meter but i bought it used and they had no instructions.i recently started a taxi business and a meter would be very useful.Does anyone know how to install a taxi meter in a 91 buick park ave?They are usually GPS synced now days so a satelltie would be able to tell the distance you moved.....Just plug it in and should work.