The feature was lost when the review pages were updated, and while it's been on the list of corrections to make for a while there's still no sign of its reemergence. Thus, for the time being, there's no way to add products to the list at will unless you find them on another member's lists.
Sorry.
John
I wish to update My Products on my CNET profile, but I can't seem to find the add button on the review pages anymore. Can someone tell me how to add to My Products - Got it and Want it lists?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic