Hardy plants will adapt to most temperatures in the summer and need to spend 6-8 weeks in near freezing conditions in the winter. It is a challenge in our climate to find a place cool enough to provide the necessary rest period, but not so cold that it damages or kills your plants. Others have to build a cold-frame attached to the house and monitor the temperature. Light is optional during this rest period. For most bonsai plants, direct sunlight is usually too much, but they require lots of light.
Artificial light works well, especially if it is fluorescent.
Ideally they would like a minimum of 12 hours light each day. Using a tray full of pebbles that you keep moist is a great way to provide the needed humidity for bonsai plants. Most bonsai likes to be misted, but not while in the direct sun and not in the evening. As with most plants, either too much or too little water causes lots of problems and disappointment. Make sure your pot has good drainage and the tray is full of pebbles so the bottom of the pot doesn't touch the excess water.