Find a Shrine Bauble in Lake Elune'ara, and take it to the Shrine of Remulos in northwestern Moonglade. Once there, use the Shrine Bauble. You must speak with Tajarri at the shrine afterwards in order to complete the trial.
For your first trial, search the depths of Lake Elune'ara to locate a Shrine Bauble. It decays rapidly, so proceed with it to the Shrine of Remulos post haste. Use the bauble at the shrine, and then speak with Tajarri there; she is one of Moonglade's most trusted wardens.
You only have a set amount of time to complete the task, and you may be competing against other druids searching for baubles themselves. Mental and physical dexterity will be critical to your success.
Good luck, [player].