To create a project using Paris/Texas, you need to install Erlang. To do so, we recommand you to use kerl. But this is not an obligation (of course) and probably the Erlang distribution that's comes with your package manager will do the job. However you need to use Erlang 17 or above. Indeed, Paris needs Cowboy 2 to serve HTTP pages and this one only support Erlang >= 17.
Once Erlang is installed, you can download the last version of paris.app. It is a utility helping you to create Paris' application. If you are familiar with Rails, it is similar to the rails tool. For more informations about paris.app, see the next section.
As you can see in the plugins section of this documentation, it is possible to create controllers with Ruby, Python or Elixir. If you plan to do so, you must install the appropriate language. See the corresponding documentation for each language.