You could place it near a south-facing window.  This will be especially challenging if you brought the gardenia inside during winter, when sunlight is scarce. One option you could take would be to supplement what little sunlight the plant receives with a grow light. The gardenia will also need to be in a room with a temperature of 64 °F (18 °C) during the day and 55 °F (13 °C) at night.  Adjust your house's thermostat accordingly and monitor your Gardenias' growth. Keep your plant free of drafts and never place a gardenia where it will receive direct force of hot hair from a furnace.  The drying nature of the heat could cause your gardenia to literally fall to pieces. Remember to use acid fertilizer to promote healthier growth.  Also water your gardenia as needed.  If you notice the top inch of the soil is dry to the touch, water until the soil is moderately moist. Check the pH of the soil frequently to ensure it stays between 5 and 6.  Use plant food specifically designed for blooming plants that prefer acidic soil.  A formulation for azaleas will work well. to increase the humidity in the room.  This is especially crucial during the winter season.  As stated earlier, you could group your potted gardenias in a cluster around a dish of water to increase humidity.  Be wary when misting your plants, however, since using direct water and a humidifier in tandem may cause fungus growth on your gardenias. You could also place your gardenias roots directly onto a tray of pebbles and water.  First, place a layer of pebbles across the tray and add water until the pebbles aren't quite covered.  The pebbles will hold the plant above water so their roots don't become waterlogged.  As the water evaporates, it will increase the moisture in the air around the plant. This will also encourage the flowers to bloom nicely. It is best to prune after blooms have fallen.  Cut away dead wood until you have reached your desired size. Now that your gardenias are indoors, they will attract many other bugs besides mealybugs and...

TL;DR in Vietnamese:
Đặt cây ở nơi có thể nhận được ánh sáng trực tiếp từ mặt trời trong nửa ngày. Tưới cho cây mỗi tuần một lần, bón phân một lần vào mùa xuân và một lần nữa vào mùa hè. Dùng máy tạo ẩm để tăng độ ẩm trong phòng. Tỉa cây vào mùa xuân để giữ cho cây có kích thước như ý. Thường xuyên kiểm tra tình trạng sâu bọ.