Does anyone know how to use Plushie Makers Kit? Thanks

I believe you can use them at Vanya's Workshop in Arctic Frost to make certain Nostalgic pets.

it's one of the items used for making plush-based nostalgic pets. you'd bring the instructions (for example, Nostalgic Devonti Instructions) and the kit to Vanya, and complete the quest (which will ask for a couple other random crafting items) to receive a nostalgic toy (so in this case a Nostalgic Devonti Toy). then if you also bring Vanya an Essence of Melody, you can combine it with the toy to transform your active pet into that pet.

you can see a list of nostalgic pets made with this kit here.

tanks