There is no lobby the HoloLens detect one another automatically. All you have to do is deploy to both of your HoloLens and run them. One HoloLens will become the host/server and the other will find it and become the client. When you hit play in the editor you should see the text changing, but in the editor it won't anchor. You can go to scene view while the editor is running and you should see a blue cube. You can kind of fake a 2nd HoloLens with your computer by adding a NetworkManagerHUD to your NetworkManager and entering the IP address of your HoloLens (HoloLens must host).
You have to wait until one of the HoloLens has anchored. You can tell this by reading the Text mesh as it changes.
If the HoloLens do not ever find one another and they both host/server then usually it is because the network firewall is blocking it. You can test and see if this is the case by using a mobile hotspot or an empty router(no internet on router).