LM4F232 coding help

hey i working on project . if i press a button, user led should on and again if i pss the same button the led should turn off . so i have written some code so can u please check and guide me how can i do that. becoz i am new to this programming.

#include<stdio.h>
#include "lm4f232h5qd.h"

int main(void)
{

int i = 0;

////////// port G initialisation for user LED /////////////

GPIO_PORTG_DIR_R = GPIO_PORTG_DIR_R | 0x04;

// SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);

GPIO_PORTG_DATA_R |= 0x04;

GPIO_PORTG_AFSEL_R &= 0x00;

GPIO_PORTG_DEN_R |= 0x04;

//////////// port M inititalisation for UP button ///////////

GPIO_PORTM_DIR_R = GPIO_PORTM_DIR_R & 0x00;

GPIO_PORTM_DATA_R |= 0x01;

GPIO_PORTM_AFSEL_R &= 0x00;

GPIO_PORTM_DEN_R |= 0x01;

//////////////////////////////////////////////////////////////////////////////////

while(1)
{

if( (GPIO_PORTM_DATA_R &= 0x01) == 0)
{
GPIO_PORTG_DATA_R |= 0x04; // Set the pin HIGH using OR operation .

for(i=0;i<1000;i++)
{

}

if( (GPIO_PORTM_DATA_R &= 0x01) == 0)
{
GPIO_PORTG_DATA_R &= ~(0x04); // Set the pin LOW using AND operation .

}

}

}

}

i am using IAR test bench.

please guide me how to initialise system clock and crysal frequency.