the brake unit you see on the traction motor is generally activated by a hand lever (located beside the operator seat), or foot operated pedal or hand lever located in the floor board area or left or right side of the front panel area.
Some trucks even have a mechanical system tied into the operator seat mount bracket, when you get off the seat it is spring loaded and the whole mechanism (seat included) will tilt forward and the linkage connected to it will activate that brake unit on the motor.

if this machine has a manual park brake lever it should be fairly obvious because the lever sticks out like a sore thumb on the truck, hard to miss. If you do not see this then check the seat, seat mount bracket area and see if it is tied into any linkage or cable that may go toward the rear of the truck.

Some newer trucks were equipt with an electric solenoid activated brake, i doubt this truck has this.

as for the main service brakes they are located in the wheels or front drive axle area like most clark lifts are.