as andrew mentioned, you will get an APIPA address by default.
If you want to manually assign IP addresses to your VMs, you do that within the OS of each VM - not through Hyper-V Manager.
Also, an Internal Switch has the Hyper-V Server attached to it. A Private Virtual Switch is VM to VM only (if you want that extra level of isolation).
Brian Ehlert
http://ITProctology.blogspot.com
Learn. Apply. Repeat.