That is funny, I got HRM for Christmas too! I did some research today.
http://www.weightlossforgood.co.uk/t...heart_rate.htm
The basic formula to find your target heartrate is...
start with 220- your age. (220-38= 182). So, your max is 182, you will never want to go above that.
For weight loss, you will want to work at 60-70% of your max heart rate (110-128)
For aerobic exercise, you will want to stay around 70-80% (128-146)
I try to do a little of both during my workouts now. For example, during a 30 min workout, I will warm up, try to say at my 65-70% range for 15 minutes, go up to my aerobic range (70-80%) for about 10 minutes, come down to 65-70% again for the remaining 5 minutes then take a couple of minutes to moving to cool down to about 50%.

Hope that helps.