Bread and using a proofer

I have a bread proofer machine and would love to make Sourdough bread. I have no idea if I'm supposed to use active yeast or follow a recipe that calls for basic Sourdough Starter, and if so, what is the difference? What purpose does the proofing machine serve? And when do I use it during the bread making process? I'm very green at bread making, as you probably have ascertained. Thank you very much. Barbara Jo