Guild Wars 2

I got this from the living world event and there is no options to ‘unlock skin’ or anything like that. If I use it will it unlock so it can be use on other back items or is it a one time use special skin that I should keep until I finalize my characters?

You have an option of storing it in vault (which will unlock the skin in the wardrobe, but destroy the item, so you will lose one free transform), or using it on the backpack you want changed (which will also unlock the skin).
Basically, if you want to get the skin unlocked in the wardrobe, you need to destroy or use the item.

It’s already unlocked afaik.

Thanks for the assistance.