Approach the silver gate until you are prompted to "Listen closely." then press the A Button.
Start the game and head to the alleyway in the upper-right corner of Inkopolis.
Check for the new mission in Inkopolis.
The Octophones are in the "Head" section, and the Octo Layered LS is in the "Clothes" section.
At any time in Inkopolis Square, press the + Button to see your Gear.
Open the box to add the DLC items to your Gear. A large brown box will appear in front of your character in Inkopolis Square.
Check for the Splatoon 2 bonus items (Studio Octophones and Octo Layered LS).
If you downloaded the Splatoon 2: Octo Expansion for free through a Nintendo Switch Online + Expansion Pack membership, be sure you are connected to the Internet and that you have selected a User that is an active Nintendo Switch Online + Expansion Pack member.
Open Splatoon 2 from the Nintendo Switch HOME Menu and select the User that will be playing.
Open Nintendo eShop and search for the Splatoon 2: Octo Expansion to confirm that it displays as Downloaded (if obtained through a Nintendo Switch Online + Expansion Pack membership) or Purchased (if purchased separately).
Make sure your game is updated to the latest version.
Restart the Nintendo Switch system by holding the POWER Button for at least three seconds, then select Power Options and Restart.
For more information, see How to Access Splatoon 2 Octo Expansion. The DLC can be downloaded as a purchase on Nintendo eShop or for free as an added benefit of an active Nintendo Switch Online + Expansion Pack membership.
The Splatoon 2: Octo Expansion DLC must be downloaded on the system to access the content.
(For example, DLC purchased with an Australian Nintendo Account will not work with a Japanese version of the game.)
DLC can only be used with versions of Splatoon 2 that are intended for the same region where the DLC was purchased.