Hi,
To connect two computers, basically both the computers should be in same network.
Without same network, those two computers can not be connected.
If you trying to connect using wireless internet connection / Wifi , then rest of the computers also needed to be connected to same Wifi.
If you trying to connect using wired LAN, then have a router, connect, each computer to the router using LAN wire, RJ45 cable.
By doing above so, you can connect rest of the computers.
But if you still need to connect other computer remotely using different Internet connection, for temporary purpose, then install TeamViewer software in both the computers, then using that application, you can see / connect another computer like taking, MSTC.
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Waiting for your Reply,
Karthikeyan S