As a new rider, any riding you do will make you fitter. Really. Unlike seasoned cyclists, you can do just about anything on the bike and it'll make you faster. You are so unfit that you don't need to "train"- everything you do is training.

So go have fun. Don't do the same loop over and over, and don't get into timing yourself or measuring your average speed. Just go ride and have fun. Go explore. Go for longer rides, go climb hills and ride down them. When you get faster, and you will if you just spend time on the bike riding around, find a group to ride with.

Save training and making a chore of it for later. You can do that stuff for a lifetime, no need to start in on it after two weeks.