A second way to approach the topic that Apollo Dark mentioned is to burn candles for both sides of a question (e.g. break up versus return of a lover) on two separate altars. We do this all the time at Missionary Independent Spiritual Church.
A third option is to burn the negative candles or candles of removal as the moon wanes and the positive candles or candles of increase as the moon waxes.
A fourth option is to burn both on the same altar that faces South, with the positive candles at the East and the negative candles at the West.
All of these methods -- in addition to Apollo's "burn one at a time advice" are traditional and favoured methods.
The point is, your work should have some thought behind it, some methodology, and it is up to you to plan your layout.
See the thread on altars in this forum for much, much more information.
To learn more about candle magic and fire safety with candles, read this book:
The Art of Hoodoo Candle Magic by catherine yronwode and Mikhail Strabo
You can order right here in the Forum by clicking on the blue Add To Cart button.