Before you can start installing Emacs 20.6 for OS/2 you will of course need to download it from Hobbes (WWW, FTP) or Leo (WWW, FTP).
FTP download with a FTP client has the advantage over browser/WWW that you can mark all files to download at once, then go away watch a video or whatever you would like to do. If you would like to do this, enter "anonymous" as user name and your e-mail address as password.
The distribution comes in four files e206base.zip, e206el1.zip, e206elc.zip and e206rest.zip all of which amount to approximately 14 megabytes. It is necessary to download at least the first three of the files, but I recommend downloading all four as the fourth one contains all the documentation and manuals
I highly recommend to download the gnuserv distribution (@Hobbes, @Leo) for OS/2 as this port of Emacs comes without an emacsclient.
You will also need approximately 50 megabytes free space on an HPFS drive for the installation and UnZip to unpack the files.
If you have never worked with the GNU/EMX environment under OS/2, you will also need to download the EMX runtime files. The most recent version as of this writing is EMX 0.9d, fix level 3. As Emacs itself it can be retrieved from Hobbes (WWW, FTP) or Leo (WWW, FTP).
Additionally you may want to install a Un*x compatible command line shell such as the bash shell (@Leo) or the korn shell (@Leo) if you are planning to use Emacs in the full GNU/EMX environment. As far as I know Emacs is able to work internally with the OS/2 shell cmd.exe, but I have never tested this extensively. If you don't plan to use OS commands from within Emacs anyhow, you don't need to care for now. You can install any shell later as well.
1)
Copy or move the four distribution files to the root directory of the drive you want to install Emacs. Emacs will be unzip'd into x:\emacs\20.6\ and I highly recommend not to change the default paths.
Be sure to read the file readme.os2 in x:\emacs\20.6\.
2)
Put the following into your config.sys:
(Replace x: with the drive which matches your machine.)
SET PATH=[...];x:\emacs\20.6\bin;[...]; REM *** Emacs 20.6 *** SET SHELL=x:/emx/bin/sh.exe SET SYSTEMNAME=ohei SET TMP=d:\temp SET TMPDIR=x:/tcpip/tmp
Also put the following lines into your config.sys if those are not already in there from your GNU/EMX installation:
SET TERM=ansi-color-3 SET TERMCAP=x:/emx/etc/termcap.dat SET INFOPATH=x:/emx/info SET HOME=x:/home SET NAME=Oliver Heidelbach SET USER=ohei
3)
Basically you are done now, all of the above is standard procedere so far. However I had to perform the following steps additionally to keep everything happy. (I guess it has to do with some paths being left hard-coded in the port):
x:\tmp on the Emacs installation drive.
fns-20.6.1.el from x:\emacs\20.6\lib-src to x:\emacs\20.6\bin.
4)
You should be done now. Reboot your machine and change to the x:\emacs\20.6\bin directory to dump Emacs with the batch file dump.cmd.
You may want to have a look at the instemacs.cmd file - call it without any arguments to see what it can do for you.
5) - recommended
Create a directory x:\emacs\lisp. Put all additional elisp packages and files into this directory. Thus you will always have the current Emacs distribution separated from additional files you install. This will save you much time when you are going to install the next version of Emacs.
6) - optional
Create a temporary directory or use one you already have for such purposes. Copy the gnuserv distribution file os2_gnuserv_r3.zip to that directory and unzip it. Copy or move the three *.exe files to the x:\emacs\20.6\bin directory. Copy or move the file gnuserv.el to the x:\emacs\lisp directory.
If you are planning to integrate the GNU Un*x style man pages into your environment, copy or move the file gnuserv.1 to x:\emx\man\man1.
7) - optional
It is also a good idea to copy all the info documentation files into one standard directory. That is probably x:\emx\info depending on where you have installed GNU/EMX. Copy or move all the info files from x:\emacs\20.6\info to x:\emx\info\. Don't copy/move the dir file as you would overwrite your current one. I recommend to copy and paste the contents of the dir file which comes with Emacs to the one residing in the GNU/EMX directory if the Emacs related entries are missing from it.