Hope this tutorial useful for you. I adopt it from this link, and modify it with my own words.
- Step 1: Install The CodeIgniter
First of all, install it to your webserver. You can install it by extract and rename it (e.g. example) to the web server folder (e.g. htdocs if you use XAMPP).
- Step 2: Rearrange Your CI Folder
Move the application folder in the system folder to the root.