The heart rate range you've calculated represents 50-85% of your heart rate reserve, but where do you work within that range? The answer may include working at a variety of levels for different workouts. The ranges you can choose are categorized by intensity:
Low Intensity - 50-60%
Moderate Intensity - 60-70%
Vigorous or High Intensity - 75-85%
Each level of intensity draws on different energy systems and focuses on different goals such as building endurance (e.g., working at a medium intensity) or increasing your anaerobic threshold and burning more calories (e.g., working at a high intensity).
One note: You may hear that working at the low end of your THR zone will burn more fat. While you do use more fat as fuel for your workouts at a lower intensity, that doesn't mean you actually burn more fat. Your goal is to burn more overall calories, something easier to do when you work at higher intensities.
Now that you have your THR zone, you need to decide how you'll keep track of it. The easiest way is with a heart rate monitor. Most come with a chest strap and a watch that allows you to see a continuous reading of your heart rate. Learn more about what you should know before you buy a heart rate monitor.
If that isn't an option, you can always periodically take your pulse during your workout by counting the beats for 6 seconds and adding a zero to get your beats per minute.
In the first step I mentioned that these heart rate calculations aren't always accurate and one way to get around that is to use both your heart rate and your Perceived Exertion.