The first for loop sweeps from 0° to 180°
The second sweeps back from 180° back to 0°
There is a function in the code that creates a small delay, (with a parameter in milliseconds) as it sweeps around
Then the loop() loops and you start over
So where do you think you could put a delay() call to pause based on your needs?
EDIT: bummer Jacques let the cat out of the bag before I clicked post 