How to configure the internal oscillator of a PIC16F616?

#include <xc.h>
__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_ON & MCLRE_OFF & CP_OFF & IOSCFS_8MHZ & BOREN_ON);

void interrupt myInterrupt(void)
{
    if (T0IE && T0IF)
    {
        RA4 = ~RA4;
        TMR0 = 254;
        T0IF = 0;
    }
}

void main()
{
    TRISA = 0;
    ANSEL = 0;

    PSA = 1; // Prescaler Assignment bit : 1 = Prescaler is assigned to the WDT, 0 = Prescaler is assigned to the Timer0 module
    T0CS = 0; // T0CS: TMR0 Clock Source Select bit : 0 = Internal instruction cycle clock (FOSC/4), 1 = Transition on T0CKI pin
    T0IE = 1; //T0IE: Timer0 Overflow Interrupt Enable bit
    GIE = 1; //GIE: Global Interrupt Enable bit

    while (1);
}