Yes, you have to go to outhouse and press "E" it will open skill management inventory. All shards are active skills/stat passives. You can check out the video on my YT about the game if you have problems with understanding what to do (don't need to watch the whole thing, you can watch the gameplay part where I explain the gameplay loop)
Oh wow, never saw the restroom, don't ask me why. Thanks! It looks really, really good. I would tune the 'hitbox' of Shrek a bit though, especially when targeting it feels like Shrek is hit even when far out of range. Especially noticing it with Puss. Really annoying. It becomes more a patience game than an agility game.
It would probably also be good to be able to break free from targeting when jumping away.