Prior requirements:-Have DLC installed (obviously)
-have completed the Getting a Clue quest
Its worth noting that you need to have completed Getting a Clue in the main story before the Radio station will pop up. People who have just started may wonder how to trigger the radio station popping up otherwise, just saying
Short version:-Listen to Valentine's Detective Agency Radio
-Travel to the Agency
-Dialogue
-Travel to the objective
-Pass speech check with the mother
-Open the safe in the boathouse and play the holotape (there is a key hidden in the picture frame on the desk nearby)
-Talk to the parents and agree to travel to Far Harbor
-Use the boat to arrive in Far Harbor
Note it might be possible to skip certain steps such as the speech check of the mother.
Detailed version: When you start up the game after installing the DLC you'll get a quest with a prompt to listen to the radio station: Valentine's Detective Agency Radio
When activated your mission will update to go to the Valentine's Detectve in Diamond City.
After some dialogue you can accept a new mission to help out an old acquaintance of Valentine. When you arrive talk to
both of the parents start searching for clues. The main clue for the next objective happens when you pass a speech check with the mother to discover that she frequented in the Boat House towards the east.
Inside the boathouse you can find a Safe with an Expert lock. If you don't have the skills or means to unlock it, look for a desk with a picture on it and examine the frame to get the key for the safe. You'll discover the holotape left by Kasumi. Make sure to play it by pressing
rather than picking it up with
otherwise you'll have to find it in your inventory under Misc to be able to listen to it.
Then return to the parents for some more Dialogue and you'll be able to use the boat. Do so and reach Far Harbor and conclude the first quest of the DLC, unlocking this achievement along the way.