How to make pin-straight the slighlty wavy (@ d ends) and somewhat thick hair?

pin half ur hair up, do small sections at a time, and do it kinda slow, go over the hair 2 or 3 times, but make sure ur flat iron isnt set to the hottest setting (if it has settings) then let the top half down and do the same thing. then when ur done use some kind of hair polish, or anti frizz gel.