I use Allegro, which is a mid version of Finale between the full Finale and Print Music. Sylvia Woods sells special font sets of Harp notation for the Finale series that are very useful.
If you are not experienced with music theory and arranging / composition techniques then I recommend the following books:
Music Theory and Arranging Techniques for the Folk Harp by Sylvia Woods
The Complete Idiots Guide to Music Theory by Michael Miller
The Complete Idiots Guide to Music Composition by Michael Miller
Edly’s Music Theory for Practical People by Ed Roseman
Composing Music, A New Approach by William Russo
How to Play from a Fake Book by Blake Neely