I've read people adding fruit to the primary, secondary, and steeped in warm post-boil, prefermentation wort. So, there doesn't seem to be a "wrong" way to do it. But the consensus seems to be you get the most fruity flavor/aroma if you add it in the secondary for a week or two. Repeated freezing and thawing the fruit beforehand also seems to release flavors and sugars.
"Brew like a monk, Drink like a fratboy"