It depends on how your reservation was made.
If it was on points and you are a member, you would call Member Services and they will note it on your reservation or direct you where to call (since you are only 6 days out).
If it was a reservation thru CRO (Disneys General Reservation Number), you would call there and they will either note it or tell you where to call.
Also, this is a phone number for OKW - 407-827-7700
Be aware though that the resort phone numbers do not really connect you to the front desk. You are connected to a Call Center, which answers as if it was the resort. They should be able to help you though. Since about 1/2 of the rooms at OKW are on first floor, unless you are checking in very late, you should be able to get first floor, even without any specific request.