How much sun is "full sun" indoors?
Aim for a spot that gets several hours of direct sunlight through the glass — typically a south- or west-facing window. Indoor light is weaker than outdoors, so a full-sun houseplant indoors needs your brightest possible position, right up against the window.
How is watering different for sun-lovers?
Most sun-loving houseplants are succulents or drought-tolerant, storing water in thick leaves or stems. They are far more likely to die from overwatering than from too much sun. Let the soil dry out completely between waterings, and ease off further in winter.