What is the Empower Plan Service Center (PSC)? And what is the link or URL?

Empower is the Recordkeeper for the UU Org Retirement Plan (UUORP).
As such, the Empower Plan Service Center (PSC) is the administrative web platform to submit and manage UUORP Contributions and Employee Data. 

How do we determine what contributions are owed for a deceased employee?
How do we add/update/remove authorized remitting admins on the Empower PSC?