Wireless Xbee Sender/Receiver Code

Hi everyone, I have two Xbees and two Arduinos coded so I can push a button on the sender and turn on pin 13 on the receiver. How could I code both of them so I can add more push buttons on the sender to turn on more pins on the receiver? You guessed it, I'm a total beginner.

Thanks!

Sender:

const int buttonPin = 2;


void setup() {
  pinMode(buttonPin, INPUT);
  Serial.begin(9600);
}
void loop() {
  int state = digitalRead(buttonPin);
 if(state == HIGH)
{
  Serial.print("1");
}
else
{
  Serial.print("0");
}
}

Receiver:

int ledPin = 13;
void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}
void loop() {
  if(Serial.available() > 0)
  {
    int val = Serial.read();
    if(val == '1')
    {
      digitalWrite(ledPin, HIGH);
    }
    else
    {
      digitalWrite(ledPin, LOW);
    }
  }
}

On the sender, you have code for reading one button and sending a pair of values based on the state of that button. Replicate that code, change the pin and values.

On the receiver, you have code for reading the pair of values, and turning on or off a pin, based on the value received. Replicate that code, change the pin number and the values.