To install CodeIgniter follow the following steps:

1. Download the latest CodeIgniter by clicking on the download link version from the official Codeigniter website.
2. Unzip the file in your htdocs folder and rename the folder to blog.
3. Set the base URL by opening the application/config/config.php file with a text editor.Example:

   $config['base_url'] = 'http://localhost/blog';

   
4. If you want to connect this project with the database, then open the application/config/database.php file with a text editor and set your database settings. Example:

   $db['default'] = array(
   	'dsn'	=> '',
   	'hostname' => 'localhost',
   	'username' => 'root',
   	'password' => '',
   	'database' => 'my_db',
   	'dbdriver' => 'mysqli',
   	'dbprefix' => '',
   	'pconnect' => FALSE,
   	'db_debug' => (ENVIRONMENT !== 'production'),
   	'cache_on' => FALSE,
   	'cachedir' => '',
   	'char_set' => 'utf8',
   	'dbcollat' => 'utf8_general_ci',
   	'swap_pre' => '',
   	'encrypt' => FALSE,
   	'compress' => FALSE,
   	'stricton' => FALSE,
   	'failover' => array(),
   	'save_queries' => TRUE
   );

5. To check CodeIgniter was installed successfully or not open the following link in your browser.
   http://localhost/blog