The xfmr corresponds to spectre's ideal transformer (see "spectre -h transformer" for more details). You can simply specify the number of windings on each side. The multiplier is a common parameter to all components in spectre, and means that you can place that number in parallel (probably little point in this case).
If you want a non-ideal transformer, you could either use the approach described in "spectre -h transformer" or build one out of the winding and core components (see "spectre -h winding" and "spectre -h core" - these are available in analogLib too), or use a VerilogA model of a transformer.
In addition, there is this paper you might find useful. The same site has downloadable copies of the models associated with the paper.