in the turn 3, you will find the dressing room in the lobby. It is to the left of the Shell-Out Machine and is accessed through a pair of sliding glass doors. Once inside, you can customize your own locker and check out a selection made by other players.
Location of Splatoon 3’s dressing room
Splatoon 3 mentions the locker room when you unlock it at level 4 and visit some shops, but it doesn’t make it clear exactly where it is. Luckily, finding this new feature that wasn’t in Splatoon 2 isn’t hard.
When you enter the lobby in Splatoon 3, you should turn right to find the locker room. Find the Shell Out machine that looks like a coin-operated gumball machine and go past its left side. You see a row of five stained glass windows under a balcony. The second and third windows are sliding doors. Press the action button near them to open access to the locker room.
Inside, you can customize your locker by hanging your clothes, weapons, posters and other decorations. You can also see what a few other players have done with theirs. The Catalog will give you more and more items to use here, and you can buy some from the General Store. So check back often to see your new decorating options.
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https://www.gamerevolution.com/guides/714580-splatoon-3-locker-room-location-how-get-your-locker Splatoon 3 Locker Room Location: How to get to your locker