This is a terrific infographic. Use it to move step-by-step into the fitness level you want. Focus on all three parts: diet, exercise, sleep!
The only thing I don’t like here is how they use “carbs” to mean empty carbohydrates, like grains and starches. Carbs include vegetables and fruits, but they are not the enemy. Vegetables and fruits are nutrient rich, so think of eating “good carb” not “low carb”.