You need:

ood quality shampoo&conditioner
Hairdryer
Hair comb
Hair elastic
Bobby Pins
Flat Iron & Heating Serum (optional)

What to do:

Wash your hair with a good quality shampoo and conditioner. Towel-dry it for 15 minutes and then blow-dry until it’s completely dried.
(optional) If you have natural curled hair, plug-in your flat iron and while it’s heating, apply heating serum to prevent your hair from any damage.
Brush your hair with a good quality comb to get rid of any knots.
Catch your hair in a ponytail using a hair elastic, then warp it around the area your ponytail starts and clip the hair with bobby pins (see pics if you’re confused).
Apply a little hairspray to make your hair stay longer.
If you have bangs clip them with bobby pins like Demi has done.