Press and hold the 'F' button to get in to the setup menu, you'll notice it says setup just above the 'F' button. Once in to the menu just use the tunign buttons to toggle through the settings, once you get to the setting which says 'PWR-IC ON' toggle it to the OFF position using the 'Band' button and you are done, you're internal amp will be shut down. This is also how you work all of the different menus, including the 5-band EQ, with the tuning, band and volume buttons.
The intructions are in the manual, you're just looking at the wrong section, but this should help out.
Hell if I know, I've known how to use the menu since Alpine started making it so I don't really bother with manuals much any more. I can check when I get to work later today and see if you want.
Also since you have the unit in, have you played with the time corrections features yet? They make the stereo really come alive. If you aren't confindent playing with them just go to alpine's web stie, www.alpine1.com , and log in to the I-personalized section to print out the characteristics for your car and it'll set most of the parameters for you. You'll probably want to use the CVA-7897 or 7898 setting due to the model changes and features since they don't have the new models listed yet.
They do have the new listing on now I put the info in and loaded it into my headunit a while ago and the music sound weird, the stereo was coming from the center of the car not from my driver sit, so I turn the time correction off, but since I just got my Amp I will go now to messure the dintance again and go to I-personlize to see if I can get it right this time.