Using candles during spell work is a common form of sympathetic magick, where the candle represents the subject of the spell, whether it is a person, object or sentiment. By manipulating the candle, it is filled with the correct energy for achieving the purpose of the spell. That energy is then released by burning the candle.
The type of candle used is of no concern, but the color of the candle is very important. The color should be chosen based on what the candle is representing.
The candle should be dressed to fill it with the energy of its subject. The most effective way to do this is by etching into the wax names, words or symbols to indicate who or what the candle represents. This is then sealed by coating the candle in oil or anointing it with consecrated water. Concentrate on the intention of the candle as it is prepared.
Most magick will require the use of multiple candles in order to represent all of the parts of the spell. When used during a ritual, the placement and movement of the candles on the altar indicate the forces acting on the released energy. (For instance, whether the energies are attracted or repelled.)
In some cases, once the candle is lit, it should be allowed to completely burn itself out. In other cases, the spell must be repeated over the course of several days or weeks using the same candles, so they will need to be extinguished at the end of each stage. When extinguishing candles, they should be snuffed or pinched rather than blown out.