If you have the geometry already defined in the Python script, there isn't really any need to save it as a VNL file, you can just drag the geometry directly to the NanoLanguage Scripter, as ZH mentions. Having the geometry in a VNL file can however be convenient if you want to reuse it several times, or import it into another script, without having to drag along the original Python code.
Thus, if you're anyway playing with the Python code, you can just add a few lines of code to generate a VNL file:
f = VNLFile("/home/user/my_geometry.vnl")
f.addToSample(my_configuration,"My nice geometry")
(obviously you have to change the filename and variable name, and the label, to match your specific script and conditions).