Understand the application from a non technical application administration perspective (if there are people whose responsibilities include its non technical maintenance).
Find out from staff responsible for maintenance:
* If applicable, How, why, when and where do they do what they do (eg access to set up new account details, new user setup, terminate accounts for leavers etc). Authority required to action this etc.
* what affect(s) does this have on the application.
* Get permission to login as an administrator and end user and try things out - preferably against a test system.