1. Place the bootanimation.zip you want to use on your sd card
2. Using root explorer, navigate to /system/media/ make sure you hit remount rw and the rename the current bootanimation.zip to something else
3.Navigate to the new bootanimation.zip on your sdcard and long press then select move or copy, navigate back to /system/media and hit paste then remount ro
4, Reboot and enjoy.