Use of composer is recomended. e.g.
composer create-project symfony/framework-standard-edition my_project_name
But you can go for a manual(simplier) installation:
First download the symfony-demo application from https://github.com/symfony/symfony-demo and unzip it in prefered folder.
Inside the folder, run the server localhost:8000
php bin/console server:run
On http://localhost:8000/config.php symfony recommends further system is configuration for enhanced Symfony experience.
Cuntinue with how to Create your First Page in Symfony