USA visa dropbox confirmation letter

[iyanu]

please i applied for b1/b2 visa category and i am going for a voluntary ministerial training program as a founder of a church with my evangelist, i have been to 3 other countries before but not the usa, i tried to book an appointment and i could get is the drop box confirmation letter with no appointment date and time on it, please what should i do? I believe a drop box is for people who have previously been given usa visa. please help, thank you

[immihelp]

You can't use dropbox.