If you’ve never performed this work before, you should work on it with your teacher. If you don’t have a teacher, get some coaching from a harpist who’s done it many times. He/she can show you the markings and tell you things you’ll never learn from the music alone. Also get a good recording and listen to it every day while watching the music so you’ll understand how the choir fits with the harp part in case you need to “catch up” with them if either they or you make a mistake. That will also give you a strong feeling for the tempo; don’t let a bully conductor push it faster than it should be so it becomes unplayable. If you don’t have the music yet, consider buying David Ice’s arrangement; it’s very playable. You can contact him through this website.
Alrene, if this helps, I have done this work to death, and I have never stumbled upon an easier way than exactly as written, with LH and RH alternating as per the direction of the stems, as much as possible.
Mel, I’ve tried to paste below an image of a natural sign next to a note, from the site wikipedia. Perhaps someone can take this image, if it appears on this site, and let us know if it can be used in combination with twxt, on this site.