Digital Input 0 Interrupt

I am trying to understand how to code interrupts. A simple interrupt routine would look something like this.

//If I want to trigger off of dig input 0 my port would be ICCSR (input capture)
//I do not know what value to set the port register so
//interrupts get triggered from the digital input
WrPortI(port address that you want to trigger interrupt, 
            current value of port, new value of port);

//I understand what is happing here
SetVectExtern3000(interrupt number,interrupt handling function);

WrPortI(IOCR,NULL,0x09); //will trigger interrupt on rising edge priority 1


WrPort(IOCR,NULL,0x00); //disables interrupt