May be examples will be best.

My PC configuration:
  No SCSI device is present.
  Primary IDE channel (reported as host adapter 0):
    master is hard drive (reported as TargetId 0, LUN 0)
    slave is not present
  Secondary IDE channel (reported as host adapter 1):
    master is hard drive (reported as TargetId 0, LUN 0)
    slave is IDE CDROM (reported as TargetId 1, LUN 0)

Here are some directly from my machine:

*REM fist I want to know how to use the program 
*REM so -h argument present in command line
METOD 5>cdspeed -h
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
Usage: cdspeed HA Tgt LUN [isg]+ NewSpeed
  HA        host adapter number
  Tgt       target number on the specified HA
  LUN       logical unit number on the specified Tgt
  [isgr]+   nonempty sequence of these three characters which have this
            meaning: i perform inquiry command
                     s perform set CD speed command
                     g print CD speed setting from mode sense command data
                     r perform reset command
  NewSpeed  required speed in KB/s to be set if `s' was specified,
            some well known values are:
                x1    176              x2     353
                x3    528              x4     706
                x8   1411              x16   2823
                maximumSpeed or simply max  65535
METOD 6>

*REM i recommended to run it without arguments too
*REM so launched without command line arguments
*REM --> this tells you what you have
*REM     CDROM drive is marked with asterisk (*)
METOD 3>cdspeed
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
Scanning host adapter 0 for CD-ROM devices...
  TargetId 0, LUN 0 - Direct-access device (i.e. magnetic disk)
    WDC AC313000R            Rev 15.0
Scanning host adapter 1 for CD-ROM devices...
  TargetId 0, LUN 0 - Direct-access device (i.e. magnetic disk)
    WDC AC11000H             Rev 12.0
* TargetId 1, LUN 0 - CD-ROM device
    TOSHIBA CD-ROM XM-6202B  Rev 1110 11/20/97
METOD 4>

*REM now I know that on host adapter 1 I have target device
*REM number 1 with LUN equal to 0 ... and the device is
*REM my CDROM (asterisk)
*REM I again ask what is my CDROM (inquiry command)
METOD 6>cdspeed 1 1 0 i
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
TOSHIBA CD-ROM XM-6202B  Rev 1110 11/20/97 --> CD-ROM device
METOD 7>

*REM well it's "TOSHIBA CD-ROM XM-6202B"
*REM now I want to know what speed it has (mode sense command)
METOD 7>cdspeed 1 1 0 g
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
Current CD speed: 5645 KB/s     Max. CD speed supported: 5645 KB/s
METOD 8>

*REM now I want to set speed of 706 KB/s (set CD speed command)
*REM there are two possibilities
METOD 8>cdspeed 1 1 0 s x4
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
Speed should be set to 706 KB/s
METOD 9>cdspeed 1 1 0 s 706
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
Speed should be set to 706 KB/s
METOD 10>

*REM now I want to ask what drive I have and what speed 
*REM it has, then set it's speed to 176 KB/s and again
*REM ask what speed it has
METOD 11>cdspeed 1 1 0 igsg x1
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
TOSHIBA CD-ROM XM-6202B  Rev 1110 11/20/97 --> CD-ROM device
Current CD speed: 706 KB/s     Max. CD speed supported: 5645 KB/s
Speed should be set to 176 KB/s
Current CD speed: 176 KB/s     Max. CD speed supported: 5645 KB/s
METOD 12>

*REM and last returning the drive to max speed
METOD 12>cdspeed 1 1 0 s max
CD Speed Changer V1.1  Copyright (C) 1998 Peter Hercek; See Version Resource.
ASPI32 installed OK; Adapter count is: 2
Speed should be set to 65535 KB/s
METOD 13>

If you want to know more read ATAPI specification - it
should be somewhere on Western digital ftp (or web).