To create a function in the Arduino IDE, you can follow these steps:

1. Define the function: To define a function in Arduino, use the keyword "void" (which means the function doesn't return anything) followed by the function name and any arguments in parentheses. For example:

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   void myFunction(int arg1, int arg2) {
     // code to be executed
   }

1. Write the function code: Inside the curly braces of your function, write your code. This code will be executed each time the function is called.

2. Call the function: To execute the function, you need to call it from the main loop or from another function. For example:

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   void setup() {
     // setup code
   }

   void loop() {
     myFunction(1, 2); // call myFunction
   }

   void myFunction(int arg1, int arg2) {
     // code to be executed
   }

Here's an example of a simple function that turns an LED on or off:

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void toggleLED(int pin) {
  digitalWrite(pin, !digitalRead(pin));
}

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  toggleLED(13); // toggle LED on pin 13
  delay(250); // wait 250 ms
}

In this example, the toggleLED function takes one argument (pin) and then toggles the state of the LED on that pin each time it's called. In the main loop, we call toggleLED with pin 13 and then wait for 250ms using the delay function.

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// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int seconds = 0;
int minutes = 0;
int hours = 0;

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("Time: 00:00:00");
}

void loop() {
  // increment the seconds
  seconds++;
  if (seconds > 59) {
    minutes++;
    seconds = 0;
  }
  if (minutes > 59) {
    hours++;
    minutes = 0;
  }
  if (hours > 23) {
    hours = 0;
  }

  // create a string for the current time
  String currentTime = "";
  if (hours < 10) {
    currentTime += "0";
  }
  currentTime += hours;
  currentTime += ":";
  if (minutes < 10) {
    currentTime += "0";
  }
  currentTime += minutes;
  currentTime += ":";
  if (seconds < 10) {
    currentTime += "0";
  }
  currentTime += seconds;

  // Print the time to the LCD
  lcd.setCursor(0, 1);
  lcd.print(currentTime);

  // wait for one second
  delay(1000);
}

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//Include LCD library
#include<LiquidCrystal.h>

//Define the pins for the LCD
LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

//define pins for timer
int seconds = 0;
int minutes = 0;
int hours = 0;

void setup()
{
  // set up LCD number of columns and rows
  lcd.begin(16, 2);
}

void loop()
{
  //Print the timer values on the LCD
  lcd.setCursor(0, 0);
  lcd.print("Timer:");

  lcd.setCursor(0,1);

  if(hours < 10) lcd.print("0");
  lcd.print(hours);
  lcd.print(":");

  if(minutes < 10) lcd.print("0");
  lcd.print(minutes);
  lcd.print(":");

  if(seconds < 10) lcd.print("0");
  lcd.print(seconds);

  //increase the time values every second
  delay(1000);

  seconds++;

  if(seconds == 60)
  {
    seconds = 0;
    minutes++;
  }

  if(minutes == 60)
  {
    minutes = 0;
    hours++;
  }

  if(hours == 24)
  {
    seconds = 0;
    minutes = 0;
    hours = 0;
  }
}