Baby grass snakes like areas with a lot of grass and near water. You should feed it small rodents and/or bugs, such as beetles, grasshoppers, ants, and mice. They also like rocks and log to move across and sleep in.
Keep it in a well ventilated enclosure with a tight lid so that it can not escape. Put a light or heat pad on one side of the enclosure, so that one half is warm and the other is cool. Provide a hiding area and a shallow dish of water.
A natural habitat with grass is ideal. For feeding, they can eat any small insect, beetles, or worms. Make sure there is water available, and provide direct sunlight or a sunlamp at some point during the day.