When I first started running, I did exactly as ADFnFuel says: just keep adding distance/time. Trying different routes can be fun, too. Joining races is a great way to stay motivated. In the UK, I did race for life 3-4 times, and in Okinawa I've done more races than I can count. Now that I am trying to get faster, and do more challenging distances, I add in other stuff: weight training, intervals, etc. I am getting faster and running longer, but at this point, most of my improvement could just be down to weight loss.
Good luck! The important thing is that you've found a type of exercise you enjoy doing.
Good luck! The important thing is that you've found a type of exercise you enjoy doing.