Forms authentication and User Roles

I am completely lost on what I need to do to create a secure login.  Can someone give me a step by step for what I'm trying to do?

Heres the breakdown....

The standard user needs to login to access either a "request" page or a "history" page.  Additional pages for managers will be "pending" and "approval" pages.

There is a central users database that holds all the username/passwords.  But the database was not designed to have roles for this app so the roles will have to be applied within the project.

I have NO IDEA where to begin, or what all needs to be done to accomplish this.

Any help is appreciated.

Thanks

JS