Once your booking has ended if you could do the following to arrange the pickup the day before your booking ends:
Seal the dress safely in the packaging it arrived in. Place the label provided to you when your item arrived on the parcel.
Go to the UPS website https://www.ups.com/ie/en/Home.page? and from there. You just go to shipping > schedule collection and then fill in the details with the tracking number provided on your prepaid return label.