Steps to follow:
1- Connect to your server via Remote Desktop.
2- Launch the "Server Manager".
3- Select "Hyper-V Manager" in the "Tools" menu.
4- Launch the "Virtual Switch Manager".
5- Create a new switch. Select the type "External", as it will be virtually associated with your public network card.
6- Give the new virtual switch a meaningful name and connect it to the public network card. (Note that the name of the public physical network card may be different than that which is shown in the screen capture below)
Your new virtual switch has now been created and may be used to connect your virtual machines.