OpenGameArt.org
The Forest of the Yellow Witch (Low intensity adventure, Loopable)
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"The Forest of the Yellow Witch (Low intensity adventure, Loopable)" by request licensed CC-BY 4.0: https://opengameart.org/content/the-forest-of-the-yellow-witch-low-intensity-adventure-loopable
Where to put it: Game credits or video description. If the entry has a "Copyright/Attribution Notice", follow that.