The first thing you should do is seek advice from a medical professional such as your doctor. They are best placed to advise you how to manage your condition. The best things you can do to promote healthy blood pressure are: Lose weight if you need to, exercise regularly, eat a healthy diet, reduce the amount of salt you eat, cut back if you drink too much alcohol, stop smoking, cut down on caffeine.
If you want more information about high blood pressure (hypertension) we recommend you take a look at NHS Choices. If you have low blood pressure (hypotension), you can find out more from NHS Choices too.