Find a Good Spot and Stick to It
Ficus trees are creatures of habit. They hate being moved. Find a spot with bright, indirect light and keep it there. They are notorious for dropping leaves when stressed, and a change in location is a major stressor.
Watering
Water when the top few inches of soil are dry. Water thoroughly, but don't let the plant sit in a soggy saucer. They are prone to leaf drop if over- or under-watered, so consistency is key.