Make sure that Wake-on-LAN is enabled on the target machines. Enter the machine BIOS and set Power -> Wake On PCI PME -> Power On. The exact names might vary depending on the BIOS version.
To enable the Wake-on-LAN feature on a machine running Windows, set the network adapter (NIC) properties on the machine as follows:
Select Control Panel -> System -> Device Manager -> Network adapters -> select the network adapter -> Properties -> Advanced:
The exact names of the controls may differ depending on your operating system.
If you cannot or do not wish to use Wake-on-LAN on some or all of the target machines, you will have to boot them into Agent manually before the scheduled time comes.
Alternatively, you can configure online deployment to the target machines.