Implementation of SPI Function-Simulink

Hello everyone, Im trying to implement this SPI fucntion in a Simulink block to stablish communication with my Arduino MEga 2560 . It's an easy function, the problem is i dont't know where to start, Ive read for several days information in Internet,seen tutroial about S-functions, but I found the info really confusing.This is my function code :

#include SPI.h

void setup() {}

// the loop routine runs over and over again forever:

void loop() {}

// This is the generic initialization function to set up the Arduino to communicate with the chip.

void SPI_init() {

// initialize SPI for the dSPIN chip's needs:
//  most significant bit first,
//  SPI clock not to exceed 5MHz,
//  SPI_MODE0 (clock idle low, latch data on rising edge of clock)  

SPI.begin();
SPI.setBitOrder(MSBFIRST);
SPI.setClockDivider(SPI_CLOCK_DIV16); // System clock: 16MHz; Stepper SPI runs at 1MHz
SPI.setDataMode(SPI_MODE0);

Serial.println("SPI configured!");
}

I would really apreciate if someone could help me out :) :)