debian missing firmware issue when installation

You have to put all directories

e.g. RTL8192E, RTL8192SU, rtl_nic and rtlwifi

into a vfat formatted usb drive. Then upon installation of debian,
it will ask you to insert it. You have to take off the usb drive
with debian installation software. Insert the usb drive with this firmware.
Next. Next. Then take off the usb drive with this firmware. Insert the
usb drive with debian installation software.

*** important ***

Then, you will encounter this error:

There was a problem reading data from the CD-ROM. Please make sure
it is in the drive. If retrying does not work., you should check
the integrity of your CD-ROM.

Failed to copy file from CD-ROM. Retry?

You have to ctrl+alt+f2 (switch to another console).

Then, mount /dev/sdc1 /cdrom, assuming the installation usb drive is
/dev/sdc1.

Switch back to the previous console. Go.