What sort of return? Do you mean you want to make a return, if so it is up to the seller . If not as described Seller supplies the return label. If just change of mind, then a private seller does not have accept a return.
Never having opened a return, I can't say for sure but I do not see how Courier comes into this.
It would have helped if you had said WHY you want to return as it makes a lot of difference to procedure, just as whether a Business or Private Seller.
