How do you convert 3 phase power to 2 phase power?

You need to have a properly sized Phase Converter Installed. What do you need 2 phase for? Is it just one piece of equipment? If so it may be is easier and cheaper to convert the equipment.

If you are looking for a Licensed electrician you can find one at www.contraxtor.com

Do you really mean a 'two-phase' system? This is an archaic system in which the phase voltages are displaced by 90 electrical degrees. Many people mistake this term for the 'split-phase' system, used in North America, to provide a 240/120-V service. If you do mean a 'split-phase' system, then you will need a single-phase transformer whose primary is connected across any pair of the three-phase line conductors, and a centre-tapped 240-V secondary. The centre tapped connection is earthed (grounded) to provide the neutral connection, and the potential of each end of that winding is 120 V with respect to the neutral. Of course, the turns ratio of your transformer must be appropriate for your three-phase supply. As the original answer indicates, this work will need to be performed by a licensed electrician.