1. Use virsh to connect to the local KVM host:
$ sudo virsh --connect qemu:///system
Connecting to uri: qemu:///system
Welcome to virsh, the virtualization interactive terminal.
Type:  'help' for help with commands
       'quit' to quit
virsh #

2. List all the virtual machines to make sure it is being managed by virsh
virsh # list --all
 Id Name                 State
  1 dns                  running
  2 webserver            running
  3 webserver2           running

2a. If the virtual machine is not currently in virsh, then define it.
virsh define /etc/libvirt/qemu/<vm-name>.xml

3. Set it to autostart.
virsh # autostart <vm-name>