TRAINING WITH A HEART MONITOR
Before getting started, a term you should be familiar with is "maximum heart rate". The term can be defined as follows: as your workout intensity increases, so does your heartrate until it reaches a pinnacle and cannot beat any faster. This is achieving "maximum heart rate".
A brand new formula has recently surfaced concerning the calculation of one's maximum heart rate. Here it is:
MALES: 214 -.8(age); for example, I am 45 years old so my rate is as follows:
214 - .8(45), 214 - 36 = 178.
FEMALES: 209 - .7(age); my  wife is 37, so her max heart rate is
209 - .7(37), 209 - 26 = 183
Here's some tips to help you train (ALL PERCENTAGES ARE PERCENTAGE OF MAXIMUM HEART RATE):

Tempo runs should be done between 80% - 90%. Strive for the higher end.

Short intervals can be done at 90% - 95%

Long intervals can be done at the same rate as tempo runs.

In between intervals, let your rate drop below 65% before doing your next interval.

For long runs, start out easy and work up to 70% - 75% for your run.

For those easy days, run at a rate og 60% to 70%.
For quick reference , the maximum heart rate (MHR) is determined in the chart below for ages 25 through 65.
Locate your gender (green), age (yellow) and MHR (blue). You're ready to go !!