Transforming Mars will be a long and complicated process. But this is exactly the type of subject that interests space researchers like Christopher McKay of NASA Ames Research Center. First, greenhouse gases, like chlorofluorocarbons that contribute to the growing ozone layer on Earth, will be released into the atmosphere. This traps the heat from the Sun and raises the surface temperature by an average of 4 degrees Celsius. In order to achieve this, factories would manufacture chlorofluorocarbons derived from the air and soil. A single factory would require the power equivalent of a large nuclear power plant.
The increasing temperature would vaporize some of the carbon dioxide in the south polar cap. Introducing carbon dioxide into the atmosphere would produce additional warming, melting more of the polar cap until it has been vaporized completely. This would produce an average temperature rise of 70 degrees Celsius.
With the temperature this high, ice will start melting, providing the water needed to sustain life. This water would raise the atmospheric pressure to the equivalent of some mountaintops. While this would be a survivable level, it may still require the use of an oxygen mask. The next step, which may take up to several centuries, would be to plant trees that thrive on carbon dioxide and produce oxygen.