diff --git a/README.md b/README.md
index f8f75e5..4f3bc81 100644
--- a/README.md
+++ b/README.md
@@ -12,13 +12,86 @@ A customizable bash prompt.
 
 + `cd ~/.config/`
 + `git clone https://gitlab.com/ceda_ei/wish.git`
-+ Add the following lines to ~/.bashrc
++ `cp wish/config.default.gie wish/config.gie`
+
+# Customization
+
+Customization of wish is done using a gINIe file (format specific to wish)
+which is an extended INI config file. The default location for config file is
+`~/.config/wish/config.gie`. The default config file is automatically copied
+over. The location can be customized using `WISH_CONFIG_FILE` variable.
+Multiple config files can be supplied as an array to `WISH_CONFIG_FILE`.
+
+Comments start with a `#` or `;` and always exist on a line of their own.
+
+Key value pairs are in the form of `key = value`. Keys cannot have whitespaces
+or `=` in them. Values can have any character as part of them. Surrounding
+spaces in values are stripped away. To keep surrounding spaces as a part of
+the value. Although, keys are case-sensitive in gINIe, wish treats them case-
+insensitively.
+
+Block names are enclosed in `[]` (e.g. `[core]`). Block names are case
+sensitive. All key value pairs after a block starts and before the next block
+begins are considered a part of that block. All key value pairs must be in a
+block.
+
+Available Blocks:
+
++ `core`: Core block configures Wish itself. Available keys are:
+    - `auto_newline`: Automatically add a newline if last line of output
+      doesn't end in newline. (0 to disable, 1 to enable)
+    - `theme`: Wish theme.
+    - `powerline`: Enable / Disable powerline. (0 to disable, 1 to enable)
++ `plugin`: Adds a plugin to the section the block is added to. All config for
+  that plugin goes there. Check wiki for details on available keys for
+  plugins. The key "name" defines the plugin to use. Plugin blocks
+  outside a section are ignored.
+
+Section names are enclosed in `||` (e.g. `|left|`). All blocks after a section
+starts and before the next section begins are considered a part of that
+section.  Blocks don't necessarily need to be in a section.
+
+Available sections are `left`, `right` for left prompt and right prompt
+respectively.
+
+Sample config file
 
-```bash
-WISH_PLUGINS=(exit_code_smiley bg_jobs date path newline vcs)
-WISH_THEME=plain
-source ~/.config/wish/wish.sh
 ```
+[core]
+auto_newline = 1
+powerline = 1
+theme = rgb_gradient
+
+|left|
+[plugin]
+name = path_powerline
+max_perc = 50
+
+[plugin]
+name = python_venv
+
+[plugin]
+name = newline
+
+[plugin]
+name = custom_text
+text = ' λ '
+
+[plugin]
+name = space
+
+|right|
+[plugin]
+name = date
+format = %a %b %H:%M
+
+[plugin]
+name = hostname
+```
+
+which results in the following prompt
+
+![](https://i.imgur.com/3iPFL5v.png)
 
 # Wiki