Hi Tom,
As mentioned by Rakesh, there isn't any doc that list down the steps from end-to-end what requires for configuring VTL. Basically you need to refer to the VTL manual for configuring the VTL to present its "media", "drives" and "robotic control" to Netbackup server. And refer to NB SysAdmin Guide to configure the devices into netbackup, you can refer to the chapter "Managing Storage Unit" of this document:
VERITAS NetBackup (tm) 5.1 System Administrator's Guide, Volume I for Windows
http://support.veritas.com/docs/268192
VERITAS NetBackup (tm) 6.0 System Administrator's Guide for Windows, Volume 1 http://support.veritas.com/docs/279265