To install Joomla, you must first meet the prerequisites of having PHP 5.2.4 or higher, MySQL 5.0.4 or higher, Apache 1.3, a MySQL database with credentials, and an FTP client. Then, you unpack the downloaded Joomla files onto your server, access the installation through your website URL, and go through a 6-step process to select your language, check system requirements, accept the license agreement, configure the database connection and site settings, and finally remove the installation folder for security.