The Help menu has only a few entries:
If you define the environment variable BROWSER so that it contains the name of the browser you like then FontForge will use that, otherwise it will try to guess something appropriate by looking at your PATH. On CygWin systems browsers that work in the windows world (as opposed to the cygwin sub-system) must be specified by a full path spec.
FontForge will search for help in either /usr/share/doc/fontforge/ or on http://fontforge.sf.net/.