The product key is on a yellow/orange sticker on the back of the CD tray inside the package.
Installation is as simple as inserting the CD and following the steps as prompted to install. It will not ask for the product key until activation of a subscription. When he activates, he needs to sign in with a LiveID (http://account.live.com) to create a subscription and then select the option to use a retail key.
Installation does not need the CD and can be performed by downloading the installer/installing from http://onecare.live.com. If installed from CD, OneCare must be activated within 15 days. If installed from the web, you are getting a 90 day free trial or 15 days if OneCare had been on the PC before.
Note that OneCare is not available for purchase or subscription in Moldavia - so support will not be easy for him to reach if needed. Support is via email until a subscription is established and when it can be validated through the support form:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
In which countries and languages is Windows Live OneCare available?
The Windows Live OneCare subscription service is available in the following countries and languages: Australia (English), Austria (German), Belgium (Dutch, French), Brazil (Portuguese), Canada (English, French), France (French), Germany (German), Hong Kong (English), Ireland (English), India (English), Italy (Italian), Japan (Japanese), Mexico (Spanish), Netherlands (Dutch), New Zealand (English), Singapore (English), Spain (Spanish), Switzerland (French, German), United Kingdom (English), United States (English, Spanish).
-steve