I learned how to do this in my neighborhood first. Accelerate to 25 mph, let you foot off the gas for a second and then tap the pedal to get 1 or 2 bars while the impg shows 100+ mpg. You can then gently push the accelerator up to 4 bars of electric only to maintain speed.

Once you learn how to do this, you then learn how to utilize the technique in your daily driving.
I like using it at the midway point between two redlights. I glide about 10 seconds before braking for the redlight. I also brake earlier so that I can regenerate as much energy as possible.

Good luck!