Edit `README.md` file.

* README.md: Rename title from `extract-green-color` to `Extract-green-color`.
[Requirements]: New section.
[Installation]: New section.
[Usage]: New section.
[License]: New section.

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-# extract-green-color
+# Extract-green-color
 
 Extract green color from a photo of LCD Writing Tablet.
+
+## Requirements
+
+* [GNU Guile](https://www.gnu.org/software/guile/) >= 2.2.7
+* [Guile-CV](https://www.gnu.org/software/guile-cv/index.html) >= 0.2.1
+
+## Installation
+
+### Install with Guix
+
+Add `tojo-tokyo` channel to `~/.config/guix/channels.scm`:
+
+    (cons* (channel
+            (name 'tojo-tokyo)
+            (url "https://git.tojo.tokyo/tojo-tokyo-guix-channel.git")
+           %default-channels)
+
+And proceed following:
+
+    guix pull
+    guix install extract-green-color
+
+### Install from the tarball
+
+To install from the tarball, proceed the following:
+
+    wget https://files.tojo.tokyo/extract-green-color/extract-green-color-1.0.0.tar.gz
+    tar xvf extract-green-color-1.0.0.tar.gz
+    cd extract-green-color
+    ./configure
+    make
+    make install
+
+## Usage
+
+To extract green color from `input.png` to `output.png`, proceed the following:
+
+    extract-green-color.scm input.png output.png
+
+To see more details, run `extract-green-color.scm --help`.
+
+## License
+
+GNU GPLv3+