vif = [ 'model = e1000' ]
vfb = [ 'vnc = 1,vnclisten = 0.0.0.0' ]
sdl = 0
vnc = 1
serial = 'pty'
usbdevice = 'tablet'
bootloader = '/usr/bin/pygrub'
kernel = '/usr/lib/xen/boot/hvmloader'
builder = 'hvm'
boot = 'dc'
disk = [ '<target disk spec here>,xvda:sda,w', 'file:<path to your ISO here>,xvdc:cdrom,r' ]
After you start the VM, open up a vncviewer to the dom0 address and you should see the install screen.