What do you mean exactly by the 'admin password'? You login to Backup Exec using an existing NDS account so you can change the password using ConsoleOne or NetWare Administrator in the normal way.
If you are referring to the login accounts (what Backup Exec uses to connect to the devices - volumes, remote servers etc.), these can be changed by using the Java Admin Console and going to 'Installation and Maintenance' --> 'Login Accounts'.
