How to make fat in body in 15 days?

Fat isn't good.: Foods to help with healthy weight gain: almonds, cashews, pecans, sunflower seeds, flax seeds, walnuts, hummus, Avocadoes, granola, trail mix, dried fruits, extra virgin olive oil, canola oil, protein shakes, protein bars, lean meats, poultry, fish, Smoothies (with added silken tofu or powdered milk), Greek yogurt (full –fat), pasta/ bagels & use of juice rather than soda.