To synchronize time in the local computer network the time server is added to the LAVClock  The server should be started on one computer. On the other computers new server with this computer name (or IP address) should be added in the Time correction tab.

To start and stop server use buttons Start and Stop. Current server running status is shown in the bottom of the tab.

For automatic server start just check Automatically start Time Server on this computer.

Port 37 opening should be available for opening in your firewall.