Activating a "Function" with a Webpage.

So I have an Arduino Uno, Ethernet Shield and a Tinkerkit Sensor Shield stacked but now im trying to figure out how to create a webpage that can activate/deactivate output port 00 on the sensor shield from a website.

I feel this is confusing trying to explain so if there is anything that you should know to help just reply.

Here is my code that i have:

#define RELAY_PIN  11

void setup(){
  
   /* Setup Serial */
   Serial.begin(9600);
   pinMode(RELAY_PIN, OUTPUT); 
   digitalWrite(RELAY_PIN, 0);
   delay(10);

}

void loop(){
  if (digitalRead(RELAY_PIN) == LOW)
  {
    digitalWrite(RELAY_PIN, 1);
    delay(3000); 
  }
}

This is what i want to activate/deactivate using a checkbox over the web:

void loop(){
  if (digitalRead(RELAY_PIN) == LOW)
  {
    digitalWrite(RELAY_PIN, 1);
    delay(3000); 
  }
}

Could someone add that to my code? Thanks. I am new to Arduino!

So I have an Arduino Uno, Ethernet Shield and

apparently, not a clue about client/server architecture or what a server does or what a client does.

A web browser is a client. It makes GET requests to a server for data to display (a web page). That data, when rendered, might have a check box. The check box might have a action associated with it. That action will trigger another GET request, usually to the same server.

The server decides what to return to the client, and what actions it needs to perform, based on the name=value pairs following the ? in the GET request.

You need to go to school.

When you are done, you'll have a much better understanding of what role the Arduino needs to have, and what the code will look like.