Jane, this is a recipe I have made many times (Sourdough Bread using Potato Flake Starter). Our son has, too. My family really likes this bread. We have substituted whole wheat flour for halp the flour with great success.

I will try to answer your questions for you, which were:

1. After putting together original starter mix, letting it sit for 6-12 hours is there a step between this and feeding it in 3-5 days?Yes, you must put it in the refrigerator. Then you can take it out in three days.CAUTION: Do NOT put a top on it tightly.

2. How soon can I use the starter?
After it has been refrigerated three days, remove it from refrigerator & let it come to room temperature. Then feed it and bake with it. Or share some with friends, including the recipe with it, of course.
If you have further questions, I'll try to help.