How to configure WordPress Multisite?

Hi Guys

How are you ?
When I try edit the wp-config.php - define(‘WP_ALLOW_MULTISITE’, true);

above where it says /* That’s all, stop editing! Happy blogging. */:

Save new wp-config.php file and reupload it to the root of website.

After that my wordpress doesnt open. I lost all my work.

I had to put the new wp-config.php on my site to my works again.

how can I do it now? I had tried 3 times is not work it all .

Please .

Thank you

Roberta Anisio