Preferable way is to use Composer:
```
composer require innocode-digital/wp-force-non-public
```
By default, it will be installed as Must Use Plugin. It's possible to control with extra.installer-paths in composer.json.

Alternate way is to clone this repo to wp-content/mu-plugins/ or wp-content/plugins/:

cd wp-content/plugins/
git clone git@github.com:innocode-digital/wp-force-non-public.git
cd wp-force-non-public/
composer install

If plugin was installed as regular plugin then activate Force Non-Public from Plugins page or WP-CLI: wp plugin activate wp-force-non-public.

To enable plugin it's required to add constant (usually to wp-config.php):

define( 'FORCE_NON_PUBLIC', true );