My ASUS i7-900 series/X58 mother board supports IETU, and I do see Autotune displayed on the main screen, directly below System Information and above Manual Tuning. On this PC, Autotune will not function unless "watchdog coverage" is supported and enabled. An option in the BIOS allows that to be enabled, although it is not specifically called watchdog coverage.
Either your CPU/mother board does not have this watchdog feature, or you will need to enable something in the BIOS, but what that is called I don't know. The ReadMe file on the EITU download page does not mention Autotune. I suggest checking the Readme file for IETU requirements or see if you can find the documents mentioned in that file regarding the use of IETU, if you can find them.
I've never tried using Autotune personally, since it attempts multiple over clock settings and reboots the PC many times over several hours, and I felt it was unnecessary to subject my PC to that.
Just so you know, it isn't showing up for my DX58SO2 either. I just checked the BIOS, and "watchdog coverage" was disabled (by default). I enabled it, but autotune still didn't show up.