Dimension of the cubes have no limitations. Z is usually the lambda dimension, which is often the number of channels. You must also give the line and scanning wavelengths for both calibration and object. The wavelength of channel 1 is the reference wavelength for the de-phased cubes. This last parameter can be changed until the phase map computation.
Velocities are necessary to compute the correct radial velocities maps.
The heliocentric radial velocity correction is relative to the date of he observation and the position of the object. This last value can be computed in the menu A of the program. Other parameters are additional information. The image scale is useful for complex functions as dynamics. It can be changed at any time and many functions don't use this value, which can be let to 1. at the beginning.