There are several similarly named products... Spray & Forget, etc. Regardless of the brand, I recommend using the type that you spray on, keep wet for as long a possible (10 minutes or so) and then allow to dry in place. The directions indicate that you should not wet the area (hose or rain) for 24 hours.
After that, periodic rains wash away the stains. In less than 8 weeks our sidewalk looks much cleaner! If it's in an area that doesn't get wet with rain you can rinse it once a week or so with a water hose to simulate what the rain would accomplish. For instance, our driveway typically has two cars parked on the concrete so even when it rains the concrete doesn't get very wet. So a week or so ago I moved the vehicles and thoroughly rinsed the driveway with a light scrub of a broom. Looks much better now.
By the way, our neighbor used a pressure washer with a special round cleaning head and it did a great job cleaning the driveway and sidewalk. I inquired and the neighbor indicated after-the-fact they would not recommend doing any pressure washing as it removes a layer of concrete. Their driveway and sidewalk is much more rough after using the pressure washer.