Aerobic exercise ("cardio"): Running, jogging, and biking are some examples. You're moving fast enough to raise your heart rate and breathe harder, but you should still be able to talk to someone while you're doing it. If you have joint problems, choose a low-impact activity, like swimming or hiking.
Stretching: You'll become more flexible if you do this a couple of times a week. Stretch after you've warmed up or finished exercising. Stretch gently -- it shouldn't hurt.
Strength training: You can use weights, resistance bands, or your own body weight (yoga poses, for instance) for this. Do it 2-3 times a week. Let your muscles recover for a day between sessions.
How Much Should You Exercise, and How Often?
Go for at least 30 minutes of moderate-intensity activity (such as brisk walking) at least 5 days a week. If you're just getting started, you can build up to that.
Or, if you're ready for it, you can make your workouts more intense (such as jogging or running instead of walking), but shorter. You could do that for 25 minutes a day, 3 times a week, for example.
In time, you can make your workouts longer or more challenging. Do that gradually, so your body can adjust.
When you work out, keep your pace low for a few minutes at the start and end of your workout. That way, you warm up and cool down each time.
You don't have to do the same exact thing every time. It's more fun if you change it up.
You'll probably be able to exercise with no problem, if your doctor says you can and if you pay attention to how you're feeling while you're working out.
Stop if you have chest pain or other sudden pain, have a very fast or uneven heart rate, or feel dizzy, light-headed, or very tired.
It's normal for your muscles to be mildly sore for a day or two after your workout when you're new to exercise. That fades as your body gets used to it. Soon, you might be surprised to find that you like how you feel when you're done.