New grass will need to be watered for 35-45 minutes every day for at least 30 days and established grass needs 35-45 minutes per week (twice a week if the weather is dry).

Best time to water is early in the morning, 5am-8am.
Do not over water established grass. The grass will let you know if it needs watering: the blades will start to curl up to protect themselves from the sun.