2 NEMA 17 steppers motors controlled by potentiometers with Motorshield v1?

Hi everybody.Following my previous post, I’m trying to control with a potentiometer the rotation speed of a stepper motor. I was successfull following the sketch/code I found on Arduino, but now I want to go to the next step, controlling 2 steppers with each having their own potentiometer, and maybe adding a button to switch them off when I want to. is it possible?
I have a motorshield v1, which has 2 L293D chip, but I’m lost how to change the code , especially how to initialize the stepper library. here is the code I use and it works great, but how should I modify it in order to connect the 2 stepper motors and 2 potentiometers?

#include <Stepper.h>

const int stepsPerRevolution = 200;  // change this to fit the number of steps per revolution
// for your motor


// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

int stepCount = 0;  // number of steps the motor has taken

void setup() {
  // nothing to do inside the setup
}

void loop() {
  // read the sensor value:
  int sensorReading = analogRead(A0);
  // map it to a range from 0 to 100:
  int motorSpeed = map(sensorReading, 0, 1023, 0, 100);
  // set the motor speed:
  if (motorSpeed > 0) {
    myStepper.setSpeed(motorSpeed);
    // step 1/100 of a revolution:
    myStepper.step(stepsPerRevolution / 100);
  }
}

that will be kind of ridiculous to buy a second Arduino Uno and having 2 identical system side by side when I’m pretty sure there is a way to make it work with a single Uno+motorshield v1.
Thanks for your help!