Hi NRLK
Um... I have to say that without a great deal of experience this is going to be *Very* hard to pull off. Documentation isn't really going to help. You need an IDM architect /BA to work through the business processes and transform them to technical specifications. From there you're going to have to get a skilled IDM resource to build it.
This is not something you should come at without experience. If you do, its going to go long and will almost certainly not achieve what you want. I really suggest you get someone who's done it before, even if its only to do the design work and provide guidance to technical staff.
I cannot stress enough how much IDM is not just an install. It's converting business process to technical outcomes. Every business is different.
Peter