Starting, stopping and restarting virtual servers can be done in two different ways, either individually or as a whole of vApp action.
To control an individual server, find it from either the Virtual Servers menu or from within the containing vApp. The current power status of the virtual server will be shown by either a green (powered on) lightning bolt, or a red (powered off) lightning bolt. You can quickly toggle the state by clicking this icon.
To gracefully restart, forcibly reset, or request a graceful shutdown of virtual server, click the Cog icon and select the desired action. The virtual server log will show you when this has been completed.
vApps can't be directly restarted like the virtual servers contained within, but vApp controls can be used to quickly power on or power off a group of virtual servers. To do so, find the vApp, which will have its current power status shown by either a green (powered on) lightning bolt, or a red (powered off) lightning bolt. To start or stop the vApp, either click the lightning bolt or select the Cog and choose the stop/start action.
NB: Forcibly resetting a virtual server, or stopping a vApp will cause a hard poweroff of the virtual server/s. This may cause some data loss if users are writing files, etc, and depending on the operating system configuration may result in a longer than usual startup time for disk checking, etc.