First, learn to cook for yourself. Avoid pre-processed stuff, especially sugars, and stick to simple meals made directly from meat, dairy, vegetables, fruits, spices, etc. Don't be afraid of fat. Avoid soda, fruit drinks, and sports drinks.
Each morning when you wake up, do 15 Hindu Squats, Crunches, Push-ups, Calf-Raises, and Planks. Every two weeks, add 10 more to your routine. Find a reliable place in your area to either jog or speed walk. If possible, also work on finding a spot you can do pull-ups. Aim for 5 pull-ups, and then add 5 more every two weeks.
Watch YouTube for muscle training exercises you can practice without a gym or weights. There are MANY. Do not be discouraged if you miss a day.