How to turn on the Search ( Module Filter ) on the Module Page.

I'd made a hand full of searches and not been able to find the answer I wanted. - like

drupal 7 turn on module search

drupal 7 search module not working


What I needed to search for though was 'drupal 7 module filter '

Either install from https://www.drupal.org/search/site/module%20filter  or like I did enable on the Modules page.