Try modifying the loop() function by encasing all it's code with a looping structure, just use a delay here, since it's gonna be short, and there is nothing going on then anyway:
// ...
void loop() {
while (1) { // loop indefinitely
/**** put all the stuff from your loop() function here ******/
delay(3000); // pause 3 seconds between runs
}
}
If the original program is nicely written, then my mod should run, wait 3 seconds, then run again. If it doesn't run correctly the second time, then some of the statements in the set up routine need to be executed between the delay() function and the end of the while loop. Try this and then figure out how to do that mod. If you want to do 'existing code modification' you should learn enough programming your machine in order to understand what the code does.
This was the closest to helping. I plugged it in and the program ran but still won't repeat itself.