How can I get my hair really smooth again?

Alright when you shampoo, use a non frizz shampoo and only put it on the roots of your hair. Then use a non frizz conditioner and use loads of it. I would recommend Tresemme anti sponge, thats what i use, but any good brand will work. Dont rub your hair with a towel, that causes breakage. Put some sort of serum in it, for thin hair thin hair theres this stuff called garnier fructis sleek and shine sheer that works really well, and spread it with your fingers, removing any knots. Don't brush or comb your hair, just let it dry. If you want, you can blow dry it using your fingers. Or, you shower at night sweep all your hair to the side and put it in a very loose braid. Unfortunately, Demi Lovato's hair probably has tons of product in it and went through a lot of heat damage to look like that, your hair will become really soft at least and not fuzzy at all.