You'll be surprised how well a little exercise works. When I first started this whole thing, I'd literally just go for a 30 minute walk in the evening, and then it gradually increased to an hour, etc.
Don't push yourself so hard that you hurt yourself, but do push yourself as much as you can.
The most important thing to remember is that this needs to be a change for life, there's no point doing something that you're going to quit in a few months and then putting all of the weight back on. That's also why it's important to find healthy foods/meals that you like, so that you can keep eating well for the rest of your life and stay healthy, even after the weight is gone.
Best wishes.