Hi, first you can estimate your maximum heart rate just by substracting your age from 220. This is not 100%, there is about a 10 beat error in this though.
You can easily measure your resting heart rate. While you are laying down, relaxed for about 10 minutes, take your pulse from your wrist for a full minute.

There is a way you can calculate what is called heart rate reserve. Substract your resting HR from your max HR. That's your reserve. During exercise, an effective range of HR is from 50% to 85% of your HR reserve. To calculate that do the following:

(0.5 x HR reserve) + resting HR
(0.85 x HR reserve) + resting HR

That's your working range.
BUT, please don't get hung up on HR during exercise. If you think 60% HR reserve is good for you and during exercise you let your HR get 10-15 beats higher, but you still feel good, don't slow down just to get your HR back down to the 60% mark. Do you see what I mean? Go with how you are feeling. Use your HR to gauge your progress, but don't let it limit you.
Hope this helps