composer install
php bin/console d:d:c
php bin/console doctrine:schema:update --force
symfony server:start
Now the Symfony's web server should be ready, so go to http://localhost:8000/ (maybe the port can be a little different depends on your configuration)
You should now be able to create an account with the Register button, the registration is done in a Bootstrap modal.
And then you can logged to your account with the Login button, the connection is also done in a modal.
Note : You must be logged in to access http://localhost:8000/user-only