How to use interrupt in Arduino uno ?

#include <SoftwareSerial.h>
SoftwareSerial gsmSerial(5,6);  //(rx,tx)

float temp;
int tempPin = A1;


#define FLEX_TOO_HI 400 //limit up
#define FLEX_TOO_LOW 250 //limit down
#define ONBOARD_LED 2 //for pump
#define FLEX_SENSOR 0 //for capacity sensor
int ledpin = 3; 

volatile int update = false;

char inchar;
int SMS_location_number;
const unsigned int MAX_INPUT = 165; // 160 maksimal kirim sms
static unsigned int input_pos = 0;
int bend_value = 0;   //NILAI SENSOR
byte smsON = 0;     //pengunci telepon on
byte smsOFF=0;    //pengunci telepon off
byte bend_state = 0;  // nilai motor
int stat = 0;          //pengunci nilai motor

int pompas=0;
int lock=0;


void setup()
{

Serial.begin(9600);
pinMode(ONBOARD_LED, OUTPUT);
delay(200);
 pinMode(3, OUTPUT); 
 delay(10);                  //10ms delay
gsmSerial.begin(9600);      //baud rate port serial 
delay(10);                  //10ms delay
GSM_Startup();              //GSM diaktifkan
digitalWrite(3, HIGH);
attachInterrupt(1, tc35i, FALLING);
//attachInterrupt(0, pompa, FALLING);


}



void SendWaterAlert(int bend_value, int bend_state){ 
digitalWrite(ONBOARD_LED, bend_state ? HIGH : LOW);}

 void esemes ()
 {
         
    gsmSerial.print("AT+CMGS=089610795984\r"); //coba kirim feedback
    delay(100);
    if ( gsmSerial.read()!= 2,LOW);
    {
    gsmSerial.print ("Motor ON ");
    Serial.println ("Motor ON ");
    gsmSerial.print("\x1A"); //ctrl + z
    delay (5000);}
    if (gsmSerial.read()!= 2,HIGH);
    {
    gsmSerial.print ("Motor OFF ");
    Serial.println ("Motor OFF ");
    gsmSerial.print("\x1A"); //ctrl + z
    delay (5000);
    }
   }


  
void pompa()
{
delay(1000);
bend_value = analogRead(FLEX_SENSOR);
//Serial.print("bend_value=");
//Serial.println(bend_value);
  {
   if (bend_value >= FLEX_TOO_HI)
    {
    stat = 1;
    SendWaterAlert(bend_value, bend_state);
    }
    
   if (bend_value < FLEX_TOO_LOW)
   {
    stat = 0; 
   } 

   if (stat==0 && bend_value <FLEX_TOO_LOW)
    {
    bend_state=1;
    SendWaterAlert(bend_value, bend_state);
    gsmSerial.print ("Motor ON ");
    Serial.println ("Motor ON");
    while(smsON!=1){
    esemes();
    smsON=1;
    smsOFF=0;
    }
    }
    
    if (stat==1){
    bend_state=0;
    SendWaterAlert(bend_value, bend_state);
        gsmSerial.print ("Motor OFF ");
    Serial.println ("Motor OFF ");
    while(smsOFF!=1){
    esemes();
    smsON=0;
    smsOFF=1;
    }
    }
    }
  }
    
  void tc35i()
{
  static char input_line [MAX_INPUT];    //static unsigned int input_pos = 0;
  if (gsmSerial.available () > 0) // 
  {
    while (gsmSerial.available () > 0) 
    {
      char inByte = gsmSerial.read ();
      switch (inByte)
      {

      case '\n':   // end of text
        input_line [input_pos] = 0;  // mengakhiri null byte
        process_data (input_line);//proses input_line 
        input_pos = 0; //reset buffer bos 
        break;
      case '\r':   
        break;
      default:
        if (input_pos < (MAX_INPUT - 1))
          input_line [input_pos++] = inByte;
        break;
      }  
    }  
  }  
}  
//---------------------------- process_data --------------------------------

void process_data (char * data)
{
  if(strstr(data, "smsdelete"))
  {
    delete_All_SMS();
  }

  if(strstr(data, "^SMGO: 2")) //peringatan kalau sim card nya full
  { 
    delete_All_SMS();           // delete all SMS
  }

  if(strstr(data, "+CMTI:"))//sms telah tiba.. sms telah tiba
  {    
    char* copy = data + 12;      // baca posisi sms
    SMS_location_number = (byte) atoi(copy);  // konfersi ascii ke int
    gsmSerial.print("AT+CMGR=");
    gsmSerial.println(SMS_location_number);  
  }                                          

 if(strstr(data, "on"))
  {
    digitalWrite(3, HIGH );    // led nya off
    delay(100);      
    gsmSerial.print("AT+CMGS=089610795984\r"); //coba kirim feedback
    delay(100);
    gsmSerial.print("SELENOID IS ON"); 
    delay(10);
    gsmSerial.print("\x1A"); //ctrl + z
    delay(10);
    delete_one_SMS(); 
  }

  if(strstr(data, "off"))
  {
    digitalWrite(3, LOW);    // led nya off
    delay(100);      
    gsmSerial.print("AT+CMGS=089610795984\r"); //coba kirim feedback
    //gsmSerial.println("AT+CMGS=089652363282\r"); //coba kirim feedback
    delay(100);
    gsmSerial.print("SELENOID IS off"); 
    //gsmSerial.println("LED IS off"); 
    delay(10);
    gsmSerial.print("\x1A"); //ctrl + z
    delay(10);
    delete_one_SMS(); 
  }
   if(strstr(data, "cek suhu"))
  {
      temp = analogRead(tempPin);
    temp = temp * 0.0306;    // led nya off
  
    delay(100);      
    gsmSerial.print("AT+CMGS=089610795984\r"); //coba kirim feedback
    delay(100);
    gsmSerial.print("suhu =");
    gsmSerial.print (temp);
   gsmSerial.print ("*C" );
    delay(10);
    gsmSerial.print("\x1A"); //ctrl + z
    delay(10);
    delete_one_SMS(); 
    
  }

}  //--------------------------- end of process_data ---------------------------

void delete_one_SMS()
{
  Serial.write("deleting SMS ");
  Serial.print("1");
  gsmSerial.print("AT+CMGD=");
  gsmSerial.println("1");
  delay(1000);
}

void delete_All_SMS()
{
  for(int i = 1; i <= 10; i++) {
    gsmSerial.print("AT+CMGD=");
    gsmSerial.println(i);
    Serial.println("deleting SMS ");
    Serial.print(i);
    delay(500);
  }
}

void GSM_Startup()
{
  gsmSerial.print("AT+CMGF=1\r");
  delay(100);
  gsmSerial.print("AT+CNMI=2,1,0,0,1\r");
  delay(100);  
  delete_All_SMS();
}


void loop ()
{
  if (update){
  analogWrite(update, true);
  pompa();
  }
  analogWrite(update, false);

 }
  
void suhu()
{
  temp = analogRead(tempPin);
  temp = temp * 0.0306;
  delay(1000);
  process_data ("cek suhu" );


}