update readme file

README.md

@@ -1 +1,28 @@
-# gp-back-to-top 
+# GP Back To Top WordPress Plugin
+The GP Back To Top WordPress Plugin allows you to create Back To Top custom for the your website.
+
+## How to Install
+
+### From source
+
+You will need Phing and Git installed to build from source.
+
+To complete the following steps, you will need to open a command line terminal.
+
+Clone the Github repository:  
+
+`git clone https://github.com/giangmd/gp-back-to-top.git`
+
+From within the checked out repository, run:  
+
+`phing package`
+
+The packaged zip file will be available under the build directory which is created under your locally cloned git repository.
+
+### You can readmore here
+https://wordpress.org/plugins/gp-back-to-top/#installation
+
+## License
+
+The GP Back To Top Wordpress plugin is licensed under the terms of the MIT License and is available for free. See [LICENSE](LICENSE).
+