Along with diet, your level of physical activity is a strong indicator of your risk for heart disease. Physical activity of any kind has many other benefits as well, such as relieving stress and increasing your energy levels. Like any muscle in your body, your heart needs exercise to stay fit.
Of course, before starting any new physical activities you need to speak to your doctor first, to find out what type of exercise is best for you. You don't have to join a gym if you don't want to, and you don't have to be an athlete to gain the benefits of regular exercise. Running a marathon might be right for some but not for most people. Add some activities into your everyday life, such as gardening or walking to the corner store, and watch what happens. Even if you've never really considered yourself an active person, it's never too late to start.
Everyone's exercise routine will be different and should include activities you enjoy, but try to work in a variety of activities to build strength, aerobic capacity, and relaxation. And don't forget to eat right to truly gain all the benefits of your newfound fitness.