OK, it probably means building a push pull, flyback, or forward converter with a transformer output that has split windings.
The first is probably the easiest to design, the second and third not so easy. There are controller chips specifically available for push pull converters (Linear Tech for example), and more generally for the latter two topologies.The most complex part of the design is usually in the magnetics, and the PCB design is not trivial either.
There is a lot of information on the web, and many of the companies that produce the controller chips or power switching devices have very good application notes.
If you haven't designed something like this before, you will have quite a bit of learning to do, there may be commercial devices available which will do what you want. You know what the input voltage is, and the output power and voltage, that should be enough for the purposes of a search. The output needs to be dual floating, so that you can connect the positive of one of the outputs to the negative of the other,
Cheers,
Richard
