When you complete a mission in Hitman 2 at least once, and earn some mastery points and mastery level, you will unlock the smuggling sites for this location. By choosing this place you can smuggle almost any item from your warehouse - dangerous items (e.g. when you enter a certain place you can search an agent) or bulky items (e.g. a sniper rifle in a suitcase).
Smuggling locations are not always very easy to spot, read carefully the description of the place you are smuggling to. They also have different dimensions, so you can't always smuggle a large item there. For smuggling items to a location and choosing a different starting location than the default one, you will unlock the trophy for each mission.