To invoke vicache.py, go into your compile cache directory and then:
# python /usr/local/skunk/util/vicache.py name_of_cachefile.htmlc
What then will happen is that either vi or whatever editor you have in you EDITOR shell environment variable will be started with the contents of the Python source that is generated by the STML compiler.
At this point, you can edit the source text, save it (or not) and exit your editor. vicache.py will then ask you if you wish to save your changes into the cache file.