You do not add icons to launchpad - they are added automatically. You can re-arrange them or delete them:
It would also help if you add some important info in your profile - you are not running iOS on your Mac, but you could be running 10.6, 10.7. or 10.8 - which may make a difference in your problems and answers.
Oops, sorry. In #1 I meant to say, "Can you successfully launch _iPhoto_ from its icon in the Applications folder?"
The reason I suggested my two steps is that I've seen situations where Migration Assistant had been run (after the purchase of a new computer and a subsequent data transfer) where iPhoto did indeed seem confused when opening it from the Dock. After running it from the Applications folder, it would then successfully open when selected in the Dock. I thought that a similarly successful launch of iPhoto from the Applications folder may indeed help the problematic launching from Launchpad.
As babowa said, icons are automatically added to launchpad. However, Launchpad only references the Applications folder (as I recall). If iPhoto had been moved from /Appllications, then _perhaps_ a question mark may have been present or remained in Launchpad. And a simple restart can often correct such oddball behavior.