Sales User is a named (per-user) license for Employee Portal. A Employee Portal installation must be completed first, then these additional Sales User steps can be applied to complete the implementation.
Architecture Overview

Basic Configuration for Sales User
Warning:
Complete Employee Portal installation first. Sales User is enabled within an existing Employee Portal installation.
Sales User is installed with Employee Portal, so no installation-specific steps are needed, however configuration is required to make the most of Sales User features.
What’s Next?
Visit the Sales User Administrator’s Guide for a walkthrough of advanced configuration and typical admin tasks.