The z4root.1.3.0.apk needs to be copied to your mobile or SD card. Then use a file manager like Astro and install the z4root.1.3.0.apk. Once that is done, it should have rooted the phone and installed clockwork. Now you can boot into your bootloader (should be installed by running te z4root.apk). Remember to do a nandroid backup first. Then proceed to wipe dalvik cashe and battery stats, factory settings etc... Now you can install your brand new shiny ICS Rom
Hollar if you get stuck!