There are actually two ways of getting Miley Cyrus curls. No matter which method you use you can start with combed and detangled dry hair... It helps if you have long bangs or a slight fringe through the front for this curly style. If you don't, that's okay.
Pull out your heated rollers-about 1-1 ½" sized rollers. Take small sections of your hair and roll them all the way up almost to your scalp. Start from one side of your head and work all the way around until all of your hair has been curled.
Another way you can get the same look is to use a large barreled curling iron with a 1-1/2" base. You just roll sections of your hair around it and only count from 5-8 seconds. You don't want to go any longer than that since the heat is damaging to your hair. Once your hair is in curls all around finger tousle them a teensy bit-very gently. Finish with a shine serum.