It should not be necessary to use the VerilogA models, since bsimcmg is built in to spectre (MMSIM11.1 contains the latest version of bsimcmg, 106.1 (as mentioned on the page you gave).
You can run the examples as provided directly in spectre (I commented out the .hdl lines, but even with the .hdl line it runs). Whether the results are as expected is another matter, but then these are slightly artificial examples.
For example: spectre inverter_transient.sp
If you're talking about ADE, you can add the model file (modelcard.nmos) directly in ADE in Setup->Model Libraries. You'd probably need to create a transistor component (based on nmos4 maybe) with the right parameters, since bsimcmg has different parameters than most MOS models (see "spectre -h bsimcmg" - it doesn't have w and l, but has w,d, nf, nfin etc).
Best is to get the models from the foundry process you're using.