To get the Squidward skin, navigate to C:Program Files\Steam\SteamApps\common\Octodad Dadliest Catch\Content\Models\Characters
From there, just copy the Characters folder and back it up somewhere in case you want the original Octodad skin back
Go up a folder to \Content\Workshop and find SquidwardSkin folder, Extract it. Open up \SquidwardSkin\SquidwardSkin\Content\Models
Go back up to Octodad Dadliest Catch\Content and paste the models folder here and replace existing files. Load up Octodad and you will have the skin!