Do I need to tie up my hair?

If your hair is long then you should pull it back off your shoulders.  Use a ponytail, bun, or swim cap to pull your hair off your neck and shoulders.

Do not put your hair on top of your head as that could make your height appear taller than it is and affect your results.

If you have an afro, use a bonnet, cap, or wrap to flatten it so as not to add height to your scan image.