It’s been a while, so I don’t know if things have changed, but we did everything through the ustraveldocs website: https://www.ustraveldocs.com/gh/en/immigrant-visa/. I think the account you have there to set an interview will also be the same one for the courier service. They (DHL) are a lot easier to get on the phone than the embassy, so we called over to ask them if they had my wife’s travel documents, then sent a friend to pick them up when they were ready.