there is no way to grow thick hair if your hair is naturally thin. they do make products that will thicken your hair up. use shampoo and conditioner for fine hair. also use all other hair products that promote thickness.
You can't grow thick hair if it's not something you were born with. Darker hair is usually thicker than light hair but bleaching your hair will make it thicker. Using thickening products can help. Blow-drying can give your hair more fullness. Layering your hair can also give the appearance of thicker hair.
The best way to make your hair appear thicker is by cutting it short and getting a lot of layers. To change the texture of your hair you will need to blow dry or use other sources of heat on it. You could also colour it.