Introduce Yourself!
General mountain dulcimer or music discussions
There aren't many mountain dulcimer books written specifically for the Child Ballads. Ralph Lee Smith's books are probably the closest thing to what you are seeking. Smith has written books containing mountain dulcimer tablature for selected ballads from Cecil Sharp's English Folk Songs from the Southern Appalachians. Among Smith's books you will find Smoky Mountain Memories, Song Treasures of the Cumberland Mountains, Folk Songs of Old Virginia, Folk Songs of Old Kentucky, and Songs and Tunes of the Wilderness Road. A number of Appalachian versions of the Child Ballads are included in Smith's books.
If you have the five Child Ballad books, you probably have only the words and not any musical arrangements since Child did not include music in his books. If you want some musical arrangements, you will need to get The Traditional Tunes of the Child Ballads by Bertrand Bronson. It doesn't have any dulcimer tablature, but it does have musical arrangements for many of the Child Ballads. However, be forewarned, Bronson's books do not include any mountain dulcimer tablature. The arrangements will have to be rewritten in tablature or you will need to be able to play from standard notation.
As you explore the ballads further, you will find multiple melodies associated with the same lyrics, so if you are looking for a specific melody to accompany your singing, your best bet is to "figure out" the desired melody on the fretboard a few notes at a time until you have what you want. If you do this I would suggest that you write it down in some fashion, perhaps in dulcimer tablature and keep a notebook or file.
One thing complicating things for a beginner is the fact that many of the old ballads are sung in one of the ancient modes, rather than in a major key. Modes can complicate things. Fortunately, the mountain dulcimer accommodates the modes through a simple retuning of the melody string. If you are trying to figure out a melody and the notes just don't seem to be there, you may have to retune the melody string and try one of the other modes. At that point, it will benefit you to become familiar with modes and how to retune your dulcimer to enable you to play in alternative modes.
Since you appear to be a new mountain dulcimer enthusiast, you will probably benefit most from one or more of Ralph Lee Smith's books. Good luck in your journey, and don't be afraid to return with more questions. There are many dulcimer players on FOTMD ready to assist you.