More on Installing Scripts
What if the one-click installer doesn’t have the application you need? You'll need to search online for other applications. An old resource for finding them is HotScripts.com, which includes both free and commercial scripts in many different categories and written in PHP and other programming languages. Github is a newer resource for finding free open-source software, including many web apps.
When you find the application you want, you will need to download it and then follow the instructions for installing it on your server. This will normally involve uploading the code to the location you want, creating a database for it, configuring a file in the application to connect it to the database, and then running the installation file.
Not all web hosts can run any application or programming language. Almost all hosts can run PHP, but some web hosts cannot run Ruby. PHP was once the most popular language for creating dynamic websites, so it has a very large number of available application, from WordPress to MediaWiki. Using a PHP script is a good choice if the script is able to handle your needs and you won’t need to custom-code that much. However, if you plan on creating an entirely new type of site, you might want to pick a language that is more “in” nowadays, such as Ruby. This way, when you (or someone else) begin the actual coding, you’ll be able to take advantage of a well-designed language.
(See The Different Programming Languages for more info.)