Prepare to do a lot of reading. The bad thing about NetBackup is all the different parts and figuring out how to proceed in learning it. It is kind of like a fishing rod with an open faced casting reel that was given to a child who promptly backlashes the reel and snarls the fishing line into a tight ball :) You have to figure out where to start.
Here is the path that Symantec uses in their training.
1. General high level concepts of NetBackup functions. master/media servers/clients
2. Basic installation and configuration and just the basic
3. GUI (use the help button) and command line usage (if UNIX/LINUX then add man pages)
4. configuring tape drives and storage units
5. configuring and managing volumes
6. configuring policies and schedules
7. performing backups and restores
8. catalog management
I highly suggest you copy from NetBackup installation CD and augment with free downloads all available manuals into one folder. The pdf files can easily be searched with the acrobat search engine for items that you want more information. Google is your friend and so are these links:
NetBackup Enterprise Server Knowlege Base and documentation and updates and...
http://www.symantec.com/business/support/overview.jsp?pid=15143
Digest reveals known problems and new functions
http://seer.support.veritas.com/docs/NBUESVR_digest.htm
table for NetBackup's Status Codes
http://seer.entsupport.symantec.com/docs/301522.htm
There are other posts in this forum with the "Where do I start" theme that may give more suggestions.