Enable multi-language search and enter the allowed search languages.
Set the locale for any space whose content should be indexed in a language
other than the system default language or its parent space language (Spaces > Settings > Space Settings > Locale).
Rebuild the search index (System > Settings > Search > Content Search > Index Tasks > Rebuild index). Re-indexing your content
enables you to search existing and new content in one of the allowed languages
that you selected for the parent space.
If multi-language search is enabled and there are more than one allowed languages,
the main search page will show an additional language filter so you can select your
preferred language when performing searches.