Using XKB symbols files

To use the XKB configuration files produced by this site, you can follow one of these routes.

Easiest Route: Patch files

In the editor for a layout, there is a link to a patch file. Download the patch file and apply it at the root of your xkb configuration. For example, on a Debian system:

$ cd /usr/share/X11/xkb
$ sudo patch -p0 < /path/to/downloaded.patch
After that, generate the layout file and place it on the symbols subdirectory of your xkb configuration. You only need to do this once (per layout).
Note:
The patch files are built for use on a "virgin" system and install the layout as a variant of the Israeli layout (il). Trying to apply a second patch file will likely fail; at that point, you should probably move to the next route.

Understand some more: Do it by hand

Stuff you only need once (per layout name/file)
  1. Add a reference to your layout from the .../xkb/symbols/il file, by appending to it lines like:
    partial alphanumeric_keys xkb_symbols "layout_name" {
      include "layout_file_name"
    };
    With this, you've set basic inclusion of your layout, and you can already use it with commands such as setxkbmap. The next steps will allow you to apply your layout using graphical tools.
  2. Go to the folder .../xkb/rules/
    In it, you'll find files named evdev.xml,base.xml
    In each of them, find the definition for lyx, and after it, add a block like:
      <variant>
        <configItem>
          <name>layout_name</name>
          <description>layout_description</description>
        </configItem>
      </variant>
  3. Still in .../xkb/rules/, for every file.xml file you've changed above, there's also a file.lst. In this file, again, find the definition for lyx and add after it a line:
    layout_name     li: layout_description
Now, to update your layout
Download the layout file and put it in .../xkb/symbols/. The layout will be available through your graphical keyboard configuration tool.

A word on caps lock and key types

The layouts produced by this site allow control of the keyboard's behavior when caps lock is on. There are four routes to go:
You don't care about caps lock
Set caps behavior to "Default", and forget about it.
You want simple caps lock behavior
Select a caps lock behavior which can be supported by the default X11 key types. At the moment, this is only the "SI1452" option. You will not have to choose a key-type for caps.
You want special caps lock behavior, and have no other use for the caps lock key
After you select the caps behavior, set "key type for caps" to "eight-level". It is somewhat of a patchy abuse of the XKB definitions, turning caps lock into a level-5 lock, but it works.
You want caps lock, and have other uses for it (e.g. alt-caps to switch layouts)
After you select the caps behavior, set "key type for caps" to "six-level". You will need to apply the six-level patch.