If you tried meditating for fifteen minutes, then one of two things probably happened:
1. Your mind kept wandering off.
2. You became very relaxed.
There's no right or wrong way, just openings for different paths. If your mind wanders then you have an opportunity to see where it is going - the mindfulness path. If you become settled and calm then you're likely to find the tranquility path opening up for you. Ultimately, these two paths lead to the same place.
You need to meditate regularly or cultivate a peaceful life to understand your mind. Once you establish a practice (however small), you will have a platform to investigate and explore. That's what I'll do next.