In addition to a flat kit you also need the knowledge of how to use it. Sooner or later you will flat and sitting on the side of the road trying to figure how to change a bicycle tire is not an ideal learning environment. There are plenty of videos on YouTube detailing the steps. It isn't hard but you need to know what you're doing. I would recommend practicing it at home so when it does happen it is no big deal and you'll be on your way in no time.