The VMware backup host must be a Windows server. Since your NetBackup 7.5.0.3 Master/Media is Windows, it could be also be configured as the backup host. Ideally you would have a separate NetBackup Media Server acting as the VMware backup host, but this isn't an option for everyone.
Basically, configuring a backup host consists of adding a fully qualified server name to the NetBackup configuration. Next, you specify the credentials that the backup host needs to access VMware -- For example, you could specify the same credentials you use to log in to vSphere client.
From the Admin Console, click Host Properties > Master Servers, double-click the Master, and then select VMware Access Hosts. Click 'Add' to configure a new backup host (aka Access Host.)
Once the backup host has been specified, expand Media and Device Management in the Admin Console, then Credentials > Virtual Machine Servers. Right-click Virtual Machine Servers and select 'new.' Specify the name of your vCenter server and provide username/password.
For more detailed information, refer to the NetBackup for VMware 7.5 Administrator's Guide.
Page 18, Table 1-1 describes the components of NetBackup for VMware (beginning with the backup host.) This is a good place to start, as understanding what the components do is important.
Chapters 2 through 5 also contain valuable information (too much to list here.)
http://www.symantec.com/docs/DOC5162
Since you're on 7.5.0.3, I'd recommend keeping the following bug in mind:
BUG REPORT: After upgrading to NetBackup 7.5.0.3 virtual machine (VMware) backups run multiple times, eventually failing with status code 196 reported.
http://www.symantec.com/docs/TECH192104