It is important to exercise for a healthy lifestyle. You don't have to exercise for a certain amount of time. Finding something you enjoy is key. Stick with it.
Three times a week, you should be aiming to complete 20-30 mins of moderate intensity activity. Moderate intensity will mean that you'll continue to be exerting yourself afterward. This type workout burns about 300 calories.
If you prefer to walk, go for 10 minute walks four days a week. Walking is low-impact and easy on the joints.
Jogging for 15 minutes three days a week is a good option if you prefer to run. Running is an excellent way to lose weight and tone your muscles.
You can start slow if you're new to exercise. Begin by only doing 5 minutes of cardio five times per week. Gradually increase the amount of cardio you do until you reach your goal.