You must have a hacked Switch in order to use these mods (fusee-gelee vulnerable or ipatched on FW 4.1.0) so if your Switch is still unhacked, you should check out this guide to get hacks on it.
http://wololo.net/2019/08/17/nintend...-overcooked-2/
http://wololo.net/2019/08/17/nintend...-overcooked-2/