If you are totally unused to training start with some really basic stuff, ie walking. Running is something the human body is designed to do, it is also one of the most common source of injuries from people doing it badly and forgetting how much impact it puts through your body. If your aim is to run, start off walking ideally at a good pace, then gentle jogging and build up from there.
You are being realistic by giving yourself almost a year, and that is to be commended. If the most exercise you have had is hitting keys and mouse buttons for a while you will have to allow for this fact for a couple of months and build up slowly.
Circuit training is good largely because it will work your whole body, you can set your own level and it requires virtually no equipment.
A simple beginners circuit is below, this is all compound to ensure hitting all of your body in a small number of exercises. You will need a towel or similar and an open door.
Warm up, walking or gentle jogging 5 minutes
Reach stretches, up, up and forward, up and to either side 5 to 10 seconds each
10 reps of each, rest only to move to next exercise, 3 times round, make the exercise easy at first. All should be slow and controlled to allow focus on technique and avoid injury.
Squats with shoulder raises. Squat down, starting the movement with hips going back, not bending the knees past 90 degrees, lift your arms to shoulder height as doing so.
Press ups. These can be done from the toes or knees, the closer to your shoulders these are on the floor the easier the exercise. A start would likely be the box press up where your hips knees and shoulders are all at 90 degrees
Squat pull ups with towel. Have your towel or similar over the end of a door have one foot either side of it about shoulder width apart, hold the towel ideally around your shoulder height. Support as much of your weight as comfortable with your hands on the towel throughout, squat down and pull yourself back up. Remember your legs are there to assist your back and arms this time, not do the majority of the work. As long as you are taking sensible weight with your arms, it is safe to squat low.
Follow this up with a 10 minute walk or jog and find some videos of stretches, these are not easy to describe in type.
This is not a wonder workout, it is an introduction to exercise that will get you started. It is also very easy to increase the intensity because it’s so basic. You can increase reps, circuits, speed (once technique is perfect) even load by wearing a rucksack with some books etc. in it.
It does however work everything in your body and there is not a lot you can do wrong and harm yourself with.
I wouldn’t expect this type of workout to last long in terms of being able to move onto something else and there are a wealth of programs suggested here once you are ready.
