You have 2 choices:
1. Purchase the NBU for MySQL agent from Zmanda:
MySQL Agent is available from Zmanda http://www.zmanda.com. For quotes or any other technical or business questions related to this agent, please contact
Zmanda at: email@example.com.
2. Use MySQL to backup to disk (info in MySQL documentation), then use NBU policy to backup the disk backup as normal file-level backup (Standard policy for Linux, MS-Windows for Windows).
The only way I have seen this done, is a using bpstart_notify script to call the mysql database backup/dump function.
Just be aware that bpstart_notify has a default timeout of 5 minutes.
This timeout can be increased, but if the disk backup is taking a long time (an hour or more) then bpstart_notify is not a good idea.
Another option would be to use OS scheduler to start a script to perform MySQL dump.
The last command in the script will be bpbackup to start User-directed backup.
For this, a User Backup schedule must exist in the Policy with a window during which user backup will be allowed.