It sounds as though you have a letter of acknowledgement from Oklahoma City
If this is so you now have I think 6 months to present yourself, the letter, your current license and medical, and photo id by appointment at your nominated FSDO, which must by in the USA.
FSDOs are all listed by region on the FAA website
You should have nominated your FSDO with your original application Oklahoma city will have sent a copy to your nominated FSDO.
When you get there it's quite painless. mine took about 30 mins yesterday and there's no charge.
