J54231 & RAGHUC,
brief the process.
1) online application and online payment (no credit card),
2) then call BCIS (forget phone #) and make an appointment
for fingerprint at local BCIS,
3) at local BCIS, do fingerprint and take photo.
I had all docs w/ m when going to local BCIS, such as
I-485, Passport, EAD, ....
RAGHUC, you can do the mail-in process if local BCIS is far from
you.
yager