Set up your Timex Ironman prior to beginning your workout so you need not make any further adjustments on the fly. Press the "mode" button of the stopwatch multiple times until you reach the countdown timer screen.
Press the "set" button once to begin the programming process, which will prompt the watch to ask how many "reps" you will be performing. Enter that figure using the "recall" and the "stop" buttons to enter the number of intervals you will be performing.
Press the "start" button when you are finished. The watch will then request that you input the number of different interval times you will require. You will need two--one for your resting period and one for your active period, so input that using the "recall" and "stop" buttons.
Press the "start" button again when you are finished. The watch will then ask you to input the length of time for your intervals. As with the other steps, use the "recall" and "stop" buttons to increase or decrease the hours, minutes and seconds until you have the length of time for your rest period. Press "start" and repeat the process for the length of time of your work period.
Press the "set" button once you have completed entering your desired number of intervals. Then use the "start" button while in countdown mode to begin your workout.