As cougie says, the easy test is whether you are able to maintain a conversation at the pace you are running.
If you are new to training with a heart rate monitor, it is fairly common to find that the easy pace required to stay within the heart rate zone is incredibly slow at first. However if you perservere you will find that you start to be able to run at a higher pace whilst keeping your heart rate at a low level.
Also, I suspect you have calculated your maximum heart rate based on the 220 minus your age formula? This isn't very reliable as real max heart rates vary widely from this, so you probably won't get accurate zones based upon it. There are a few books available that can help you get the most out of heart rate training, so it may be worth investing in one.