For VMs in a pool, you can choose where to start your VMs, subject to available resources on the selected host server. Your choice of server depends on how the VM and the pool are configured:
When the VM is up and running, its status indicator changes to in the Resources pane.
Select the VM in the Resources pane and then click Start on the Toolbar.
Alternatively, do one of the following:
In a WLB-enabled pool, this will start the VM on the optimal server.
In a pool without Workload Balancing configured, this will start the VM on its Home Server, or on the first available server, if no Home Server has been set.