Keeping a fuchsia over the winter can be a challenge, but here are some ideas that will help you be successful.
Fuchsia likes humidity, so using a pebble tray under the plant will help to maintain a cloud of humidity around the plant. Indoors in the winter the air is usually very dry because of the heating system in your home, a pebble tray will really help the plants. A pebble tray is just a shallow dish full of pebbles and water that the plant sits on (not in the water).
High light is good, essential for good growth over the winter, but avoid a hot dry window where the plant cooks during the winter. In general the brighter the better for most windows just check to make sure it is not burning the plant.
Keep an eye out for spider mites, they are going to be your biggest problem. You can see them forming webs between the leaves and the leaves themselves will get a silvery look to them as the infestation gets worse. You can prevent them with frequent washing of the plant (put the plant in the shower under a gentle mist about every third watering), misting the plant will also help, but you may need to resort to some kind of organic insecticide to keep the worst infestations under control.
Over the winter keep removing any stems that start to die and remove all those berries once they begin to wither as they are actually stealing nutrients from the plant, but you can leave them on for awhile if you like them.
On watering and fertilizing: Generally fuchsia likes to be moist at all times but not soggy, so watch to make sure the plant does not dry out too much. Fertilizing every 6-8 weeks with half strength fertilizer should be fine to keep the plant healthy.
Your local state extension service will likely have a lot of good information on over-wintering houseplants as well, so check their website to see if they can answer questions that are local to your garden!