Control 2 ESC with a potentiometer with arduino
If you want one potentiometer to handle BOTH ESCs' speed, you could use this code:

//Using servo library to control ESC
#include &lt;Servo.h&gt;

//Starting the servos
Servo esc1;
Servo esc2;

void setup() {
    esc1.attach(9); // Use a PWM pin to the Servo, in this case 9
    esc1.writeMicroseconds(1000); //initialize the signal to 1000
    esc2.attach(10); // Pick another PWM to the other, in this case 10
    esc2.writeMicroseconds(1000); //initialize the signal to 1000

    Serial.begin(9600);
}

void loop() {
    int val; //Creating a variable val
    val= analogRead(A0); //Read input from analog pin a0 and store in val
    val= map(val, 0, 1023,1000,2000); //mapping val to minimum and maximum(analogRead's goes from 0-1023 and analogWrite's goes from 0-255, check your servo's specs)
    esc1.writeMicroseconds(val); // write to the first ESC
    esc2.writeMicroseconds(val); // write to the second ESC
    delay(100); // We usually set a small delay to avoid excessive readings or over-heating, but thats optional...
}


If you need to use two potentiometers, one for each ESC, then you would have to start another variable to read the 2nd pot value and use it to write on the 2nd ESC, simple as that! :)