First change the password for the user BISystemUser in the realm.
Then, from Fusion Middleware Control target navigation pane, expand the farm, then expand WebLogic Domain, and select bifoundation_domain.
o From the WebLogic Domain menu, select Security, then Credentials.
o Open the oracle.bi.system credential map, select system.user and click Edit
o In the Password field, enter the user's password that you used in the realm
o Click OK.