I realize that some of you may be complete beginners at exercise. Don't worry about catching up! If you want to run, don't jump in right away. I did that and now have knee problems. Start slowly and build your endurance. Then you can add more activity at your own pace. Here is a simple routine that will help get you started.
Walking. Walk 30 minutes 3-4 times a week at a pace that's comfortable. Don't be afraid to push yourself a little, though. But make sure you are going at a pace that will allow you to finish 30 minutes. Increase your pace and the time you spend walking as you are able.
Abs. Situps are great. Do as many as you can, but aim for 3 sets of 15. Make that your goal!
Pushups are a great upper body toner. Do them against a wall, on your knees, or on your toes depending on your ability. Aim for 3 sets of 15 as a goal.
Add things to your routine as comfortable. But this will provide you a good base once you want to up the intensity.