if you can edit the main php.ini file, change the option to on:
then reload the phpinfo page to see if it applied. The location of the file is defined in the Configuration File (php.ini) Path of the phpinfo view. If you cannot edit the main php.ini, you can try to create a new php.ini file in the document root. And just add the options you want to change. The Loaded Configuration File field of the phpinfo view should show if the new file is loaded.
Note: some times, the configuration (of PHP or of the web server) does not allow to override the settings through custom php.ini files, so you may need to contact your hosting support to make changes.
For more info, see the HOST and PATH directives: