All DMR calls have a source and destination ID, and calls can be private or group. The source ID is set to your DMR ID by your radio, and the destination ID is usually the TG you want to call (in case of a group call) or the private DMR ID (in case of a private call).
Make sure you send your calls to 9999. Private or group call does not matter, the OS2 will answer both with a private call back to your ID (so you'll be able to hear the echo reply no matter of your TX contact or RX group list configuration).
Now there is a DMR usage info page in the user manual:
http://manuals.sharkrf.com/openspot2/en/dmr-usage-notes.html#page-top