You will need to add a logic level mosfet of the appropriate size and specs to control the power to the motor. You can drive the gate of the mosfet from a pin through a current limiting resistor with a larger bleed resistor. For a brushed motor you'll need a ceramic RF supressor cap plus flyback diode for back EMF protection:
simulate this circuit – Schematic created using CircuitLab
For greater RF supression (if your motor is pretty beefy) you can use a 0.1uF between each input lead and the motor case.
When you turn the pin on, motor turns on, low turns off. Using analog and appropriate R values you can control motor speed (setting 0-255):
int motorControl = [your pin];
delay(10000); // delay 10 seconds plus board boot time
analogWrite(motorControl, 255); // turn motor on full
You can time the delay with a stop watch and adjust to be exactly 10s by dropping the delay() call to compensate for the boot up time of the board.
More about MOSFETS here: