You can use this connector to connect to a network which supports the Dplus protocol like REF or XRF.
The easiest way is to use the Quick setup to connect to these networks.
If you want to use a reflector, set the URCALL on your radio to CQCQCQ. If you want to use a gateway, set the URCALL to the gateway's callsign and remote module. Remote module should be the last character of the URCALL.
Note that if you are connecting to a repeater, you have to set the Reflector/gateway ID connector setting to the callsign of the repeater.
REF and XRF servers need a valid D-STAR registration. You can check your callsign's registration by clicking on the Check D-STAR registration button. Make sure you have registered your local module on the D-STAR gateway registration system. If you have a registration, you have probably registered the "space" local module, in this case set your openSPOT2's local module to a space (empty) character.
Try remote module E on any reflector for the REF/XRF echo service (may not enabled on some servers).
You can switch reflectors using your radio by starting a short call to their names as the destination callsign (URCALL), like REF001 A, or XRF001 A. You can also switch to DCS/XLX servers by this method - switching this way changes openSPOT2's active connector.
As the openSPOT2 is designed to be always connected, the unlink (U) command is not interpreted. If you really want to disconnect, you can switch to a config profile which has the Null connector activated.