Iva's notes probably will be more helpful but I do have a project you can review and test on FRDM-K64F attached.
Note/comments in the main.c. Look for "//DES".
Unzip to following folder:
C:\NXP\KSDK_v2\SDK_2.0_FRDM-K64F_KDS\boards\frdmk64f\user_apps
Regards,
David