How can I lose weight without exercising?

You don't need to exercise to lose weight - though it will help.

Set your activity level on MFP as sedentary and set a reasonable goal (depending on how much you have to lose, 0.5-1lb per week). Eat the calories you're then given as that number does NOT include any exercise whatsoever.

~Lyssa

1) Track what you are eating (get a food scale so you are accurate)
2) Weigh yourself regularly (daily or weekly, more often if you need more focus, less often if you start obsessing about the number)
3) Start to reduce gradually until you are losing weight

"Most weight loss occurs because of decreased caloric intake.
However, evidence shows the only way to maintain weight loss is to be engaged in regular physical activity."

http://www.cdc.gov/healthyweight/physical_activity/index.html

This calculator from the Baylor College of Medicine will tell you not only your BMI, but how many servings of various foods to eat to maintain a particular weight. It takes into account, height, age, plumbing, activity level.
You could put in your goal weight, and if it's in the healthy BMI range just eat at that level.
https://www.bcm.edu/cnrc-apps/healthyeatingcalculator/eatingCal.html

I broke my pelvis seven weeks ago and I was worried that I would gain weight while sitting around. I stuck to my calorie allowance and I lost nearly two pounds per week. I'm a little out of shape now, but I'm also lighter.