Any object maybe used as long as it remains very still in front of you, and it is relatively small to the gaze. A candle is the most convenient and most recommended object for this purpose, as it is easy to evoke its image when you close your eyes. Stare at a candle in front of you without blinking, and for as long as you can, then close your eyes and try to see the candles image in your mind. When it begins to fade from your mind, open your eyes again and stare unblinkingly at the candle.
Start with a 5 min session, then gradually increase the time to half an hour, and then up to an hour. Your mind is a fine instrument, like a violin it must be handled with great care and appreciation, then eventually its music will astonish you with its beauty, its range, and its genius.