There is a Guest OS Customizations tab on every VM created from a catalog Template... By default it is greyed out and the admin password is auto generated. How do I change the settings on this tab? Do I need to do something at the system level?
If you are a System admin, or a Org Administrator you can change these settings on a Vapp (not VappTemplate) that is currently in a Powered Off state. (Not just the VM's need to be off, but the vApp needs to be stopped as well if I recall correctly)
You also need to make sure the sysprep packages got setup correctly on your cloud cell (part of the install guide).
Another quick note, if you have more than one cell and do not have a load balancer in place guest customization will fail for some reason. But if you have only one cell this would not be an issue.