You can also set the password by browsing to Advanced Settings, or from bash using the appropriate setting commands:
[root@lorne14-pro tftpboot]# fwconsole setting --list | grep MGR
| AMPMGRPASS | <redacted> | amp111 |
| AMPMGRUSER | admin | admin |
[root@lorne14-pro tftpboot]# fwconsole setting AMPMGRPASS new_ami_password
Changing "AMPMGRPASS" from [redacted] to [new_ami_password]
[root@lorne14-pro tftpboot]# fwconsole setting --list | grep MGR
| AMPMGRPASS | new_ami_password | amp111 |
| AMPMGRUSER | admin | admin |