Greetings, Greg. While combing the archives might give you a few hints, I suggest that you take a look at this primer by Robert Kelley:
http://www.robertkelleyphd.com/ShapeNoteMusic/SacredHarpHarmonyPresentation.pdfIt was very helpful to me. I also learned a lot by looking at tunes in the our tune books to get an idea of things like range, tesitura, etc.
In terms of software, you might want to check this out:
http://home.olemiss.edu/~mudws/resource/chap12.htmlI personally use Finale, but it is very expensive and would be overkill unless, like me, you do a lot of notation of more "normal" music. The same would be true of Sibelius and Dorico. Some of the people on this list swear by Lilypond while others use Harmony Assistant. I haven't used it, but I've heard good things about Musescore. I'm not aware of any notation apps for iOS or Android that handle shape notes, but most of the major ones, such as Notation Pad and Notion allow you to export your music in MusicXML format that you can then upload into a desktop application such as Musescore.
Hope this helps. Good luck with your first tune. Hopefully we'll get a chance to look at it when you feel it's worth sharing.