Can I display my outdoor bonsai inside the house? How?
Yes, you can bring your bonsai inside - but not permanently - and it must be ensured that they are given extra-special attention. Generally you should only keep your bonsai inside for more than 3 days a month at most. You can not grow them inside (that follows into the realm of indoor bonsai which uses a completely different group of plants).
You may wish to display your bonsai when you are having a special occasion or to admire their beauty when they are flowering or fruiting, but it is not advised to bring them in too often - for risk of causing undue stress to the plant.
Care must be taken to ensure that they are given the right amount of water (definitely not allowed to dry out) and sunlight as well as humidity which can be achieved by misting with a general water sprayer. Make sure that the bonsai are not positioned in the way of any draughts and definitely not next to a heater - even in winter. Above all, the bonsai should not be disturbed too much from their general routine.
If you want to keep your bonsai warm during the winter (i.e. if they are tropical bonsai) - a heater can be used - but you must also use a humidifier to keep the plants from drying out. Do some research beforehand on the species of your bonsai before you decide if you want to do this