Exercise out doors as far as possible. There are two advantages of doing whatever you are doing out side. One advantage is that it gives your body a chance to get a lot of the much needed fresh air and sunshine.
The second advantage is that the surroundings keep you perked up and it is a break form remaining cooped up all day long
Try to collect some information about exercise, there are a lot of things that you can do at home. Extensive research has been done on exercise and plenty of this information is easily available.
You can try browsing the net or getting a book or two on how to exercise at home. This information will be useful to you to know how much you need to work out on each specific exercise in order to burn off the desired number of calories.