On this page of The Witcher 3 Wild Hunt guide you will find walkthroughs for the main quests Missing Person and Nameless - these are quests available on the Skellige Isles. The following walkthrough explains whom Geralt must meet in the village of Loften, how to get to the Freya's garden, and how to go through the garden.
After completing the Echoes of the Past quest, you can automatically transport with Yennefer to Loften, where the Missing Person quest starts automatically. Alternatively, you can meet Yennefer there later.
In this quest you must only talk to the women in the middle of the village. They will point you to Freya's garden North from the village. Follow the sorceress there.
Once you reach the garden, the quest will end, and another one will start: Nameless. When you arrive, the main entrance to the garden will be closed - follow the sorceress to the walls near the tree, there you will see a track that leads to the garden.
Inside you will find wolves (level 14). After walking down, turn left and go forward until you see a lever. First activate the right one, then the left one - a hatch will open and you will be able to swim through the sewer to another part of the garden.
There you will find a well. If you examine the nearby house, you will meet werewolf Morkvarg (from the In Wolf's Clothing side quest). You don't have to fight him yet. The full walkthrough for this quest can be found on the page about side quests on the Hindarsfjall island.
Just jump to the well and you will find the body of the Coward. A moment later Ciri's story will activate - The Calm Before The Storm.