The command M-x muse-project-publish-this-file will publish the current document to any available publishing style (a publishing style is an output format, like HTML or Docbook), placing the output in the current directory. If you are in Muse Mode, this command will be bound to C-c C-t. If the file has been published recently, and its contents have not changed, running C-c C-t again will not publish the file. To force publishing in this case, do C-u C-c C-t.
If you have set up projects and are visiting a file that is part of a project, then C-c C-t will restrict the output formats to those which are used by the project, and will automatically publish to the output directory defined by the project. If you want to publish to a different directory or use a different format, then use C-c M-C-t, which is also M-x muse-publish-this-file.
If the currently opened file is part of a defined project in
muse-project-alist, it (and the rest of the changed files in a
project) may be published using C-c C-p.