Step 1: Log into your cPanel account
Step 2: Download latest version of CodeIgniter from the below URL and save it in your local computer.
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https://codeigniter.com/userguide3/installation/downloads.html
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Step 3: Upload the CodeIgniter zip file on installation directory of your cPanel and unzip the package.
Step 4: Upload the CodeIgniter folders and files to your server. Normally the index.php file will be at your root.
Step 5: Open the application/config/config.php file with a text editor and set your base URL for your website.
Step 6: Create database from the cPanel >> Database , open the application/config/database.php file with a text editor and set your database settings.
Step 7: Once you have completed the installation, start edit your website as per your requirement.