It should be on your confirmation letter. I used the address from those letters for our recent trip. I had water shipped from Costco to OKW and also BCV. I went with the addresses from those yellow letters. Worked fine.
Well I ordered some water to be sent to OKW about 2 days before we left and it arrived two days after we got there. I ordered water the morning we left which was a Sat. and we weren't checking into BCV until the next Sunday..so a week an a day later and it arrived BCV on Thursday....we checked in on Sunday. I didn't even inquire about it til Monday or Tuesday ...it was still there.
I ship a box everytime we go and the resorts will hold it until you pick it up as long as the designation is made on the package somewhere, who it is for and if possible, the arrival date. Every front desk has told me that this is the best way to make sure you get your stuff.