How do I start with developing and idea I to a product.

Without getting too detailed, I have an idea for a peice of business management software that I want to get developed and sold. Where do I start? I work in IT as a network and voip infrastructure administrator. That being said I wouldn't even know where to begin with creating a peice of software, package it, and license it's use.

For starters, there wouldn't be any cloud connection, everything would be run local.

Any pointers on where to even start? Right now it's a detailed and complex requirement that's sitting on paper.