go to PVS server and open Provisioning services console
Farm > Sites > Site > vDisk pool
right-click vDisk > Versions ...
click New
clone one of the VMs using the vDisk in vCenter and take note of its MAC address
right-click on the collection using the vDisk and create device
change type to maintenance and enter MAC address of the freshly cloned VM
make sure to attach correct vDisk
right-click on the newly created machine in the collection list to create its AD account
start the maintenance VM and select [maint] vDisk from boot menu
make desired changes (install new app, change wallpaper, windows updates, ....)
always make sure there is a graceful shutdown of the VM << Locks
go to PVS, locate vDisk, right-click vDisk > Versions ...
promote (production, immediate), click OK - all VMs will start using this version
merge - make the new version "base" one

Automating vDisk updates:
PVS Console > Farm > Sites > Site > vDisk Update Management (works w WSUS & SCCM out of a box)
Hosts - right click - add (ESX/Hyper-V,XenServer) ...
add vDisk (clone one of vDisk's existing VMs, will need to enter its name)
check AD account for VM or right-click on the vDisk > Active Directory > Create Machine Account ...
right-click Tasks > Add task
Site > Properties > vDisk updates - check Enable automatic vDisk updates on this site
alternatively you can change auto update settings for an individual vDisk > Properties

Setting to keep in mind:
Farm > Properties > vDisk version