Do you have any place to plant it outdoors? If not, then this should be treated as a flowering temporary houseplant (much like azaleas and hydrangeas are sold as such). Keep away from strong sunlight and water often enough to keep the soil just moist to the touch. Do not let the pot sit in water.

Unfortunately, lily flowers indoors do not last very long. And once that plant has finished its current flowering, it will not bloom again. If you have no way of planting outdoors (or even in an outdoor container), then there is no point in keeping the plant after the flowers have finished.