This area allows the project admin to associate the previously added users to a Vendor/Supplier Package.
There are four types of users that an admin can associate: Vendor, Reviewer, Consolidator and Approver depending on their role within a workflow on a project.
You should only assign a single Vendor. You can assign multiple reviewers, preferably one Consolidator and one Approver.
It's important that the Project Admin keeps a matrix of users and roles, this will assist in assigning new passwords and roles.