Does your new alternator need to have voltage going to from someplace before it will put out any juice?

Most alternators need a voltage present to operate. This is because the voltage is used to create the magnetic field used to generate power. If you are directly replacing another alternator, the wiring should already be correct for it. If you think that your alternator is not receiving power (for its field windings) then you should check for the presence of the voltage with a meter when the ignition switch is on. The proper place to check will depend on the vehicle, and some newer alternators will only apply the voltage when a start signal is recognized. This would make troubleshooting much more difficult.