If you don't succeed, here are the instructions I figured out. The procedure seems a little bit outdated, to be frank. It's quite understandable you don't understand it, I would say.
The file you donwloaded (I found userman_p660_na.zip, which I think is correct also) contains 1 file, called oum660-1.exe. It's a self-extracting file, so if you run it, it asks where to put the files it contains. I had created a folder c:\download, so that's what I filled in. That gave a subfolder tinstall, that contained a subfolder oum660, and that contained 4 files: online1.exe, online2.exe, online3.exe and readme.txt with the instructions.
The full text of the readme file is ''Toshiba Portege 660 Online User Manual unpack the 3 files to disks and install manual with the SETUP on disk 1''.
To continue you should have 3 1.44 Mb diskettes first. Then go into a command window, put in the first diskette, cd to the download\tinstall\oum660 folder (or whatever you called it) and type online1 (+enter). This should show something like:
''Disk eXPress Self-Extract Diskette Image (OS/2 and DOS)
Version 2.10a 02/12/93 Copyright (c) 1991-93 SHAREWARE VERSION
Usage: ONLINE1 [/t] [drive:]
/s Suppress overwrite prompt
/t Test image integrity only
drive Drive letter of a valid floppy disk drive
Note: The target diskette must be formatted and must not have any bad sectors.''
which shows that you should type the following command:
Same for online2 and diskette #2 and online3 and diskette #3.
So now you have three diskettes. Diskette #1 contains a file setup.exe. So put in diskette #1 again, type
and follow the instructions.
Piece of cake, in fact.
I looked up the specs of this machine in http://cdgenp01.csd.toshiba.com/content/ product/pdf_files/detailed_specs/portege_660cdt.pdf
Seems like a nice 1996 laptop. Intel Pentium 150, 16 Mb EDO RAM (extendable to 80 Mb), 11.3'' color TFT display, 1.35 Gb hard disk, internal 28.8kbs modem, sound card. User selectable either DOS 6.2/Windows 3.11 or Windows 95. Comes with AOL, Compuserve and Netscape Navigator.
Personally, I wouldn't spend $129 for such a machine, offered at http://www.bedfordmicro.com/item/view?item_id=1864, I think. But there must be people who do, or it wouldn't be offered.
Can you tell if you managed to buy the manual somewhere? And it might be interesting to know why you need it after all those years.
Hope this helps. If you really don't succeed, and have a good story, I might be willing to do the job and send you the result. I'm practically halfway now. And I have some spare diskettes.