How to Configure Hyper-v LAN switches for VM's ?

Go to Actions - Virtual Switch Manager and it depends what are u intend to do? You can basically create3 types of Virtual Switches (External- Internal- Private). Either of these have its purpose and intention. 

When u Adding External You are connecting it to live Network Card that is inside of Your Server (You can add External Switches on Your available Network cards.)

Private switches creates communication inside one host, cannot communicate if they arent inside same host. And also they cannot communicate with host.

Internal network however is different (It adds Icon in network interface) so You can add and configure IP and DNS cause it has its own. It communicate with VM and Server but You cant communicate with other networks.