It's going to take a lot of patience.

I would advise starting off absurdly slow, depending on where you are now. If you haven't exercised in years, then just a few repetitions of something very non-stressful like side bends, twists, and maybe a situp or two.

Then give yourself a few days to see how it affects you. This is something you are going to have to figure out for yourself. Think in terms of months to return to some degree of fitness...a lot of months.

I've found morning exercise is much better. It gives your system time to get past the hyper stage by bedtime. I've found there is a hyper stage, a feeling of exhaustion at times, then a good feeling, then a need to rest. It cycles through over several hours.

You will likely have to put up with some feelings of malaise. Most people stop exercising when that happens. I think that's a mistake. I rest and recover, then get back to it...depending on how strong the reaction is to the exercise.

After a few months, you should see more energy during the day, a bit more strength depending on the kind of exercise you are doing, and much improved sleeping.

Don't forget resting, even if you feel like you want to take advantage of the boost in energy and keep going all day. I've found that leads to problems.

It sounds like a total contradiction, but exercise for me is an imperative part of staying on top of CFS. I will give you some advice on how to prevent a flare up, as soon as you finish your exercise jump in a cold shower, studies show that 4 minutes is best, it really helps prevent the post-fatigue.

I did 80 metre sprints after weight training last night, and after wards I spent 20 minutes in a bath full of ice, now there is no fatigue at all.

When I took phys ed, they taught us to wear warm-up jackets after exercise, so this is a little confusing to me. I don't doubt that the ice baths work, in fact I've found cool showers to be very helpful in combating fatigue and malaise.

Many years ago I got some information that cold baths would cure ME.
At first, I got improvement. Then, one day, while lying in the cold water I suddenly got scarily ill. Since then, I've been quite careful about exposing myself to cold water. At the slightest sign that this illness is returning, I turn the cold shower off. And I'd never try a cold bath again.

I mentioned this a week or so ago wathappy. Poor thermoregulation is often a major factor in CFS. If people take the time to do their temperature three times a day, they may have an idea of their temperature control. Although their is a potential benefit in terms of muscular anti-inflammatory effects, the upshot for CFS patients is a very real risk of hypothermia and infection. Contrary to a belief that heat is bad, the bodies natural defense against an infection is to raise the core temperature, hence the fever.

Isn't it so confusing that what can drastically help one person may give someone else a severe flare-up? If I could give you any advice, take the exercising very slow like the others said. Even start with stretching if working out scares you too much, then maybe transition into walking. I would also reccomend that when you do start this, since it seems you aren't sure how your body will react, do it on a day that you know you will have few responsibilities in the coming days- just in case it does wipe you out too much. Eventually you will find your balance and know how to work exercising into your schedule. Good luck.