Elevated Product Search ships fully translatable, with Spanish included in the box. To use it in Spanish, set Settings › General › Site Language to Español: the admin and every storefront label switch, with nothing else to configure. For any other language, translate the plugin with the free Loco Translate plugin. On multilingual sites, WPML and Polylang are both supported, including the text you type yourself, which Product Search registers for translation automatically.
The Spanish translation ships inside the plugin (languages/elevated-product-search-es_ES.mo). Go to Settings › General, set Site Language to Español, and click Save Changes. To keep the site in another language but use the admin in Spanish, set the Language field on your own profile under Users › Profile instead.
Loco Translate is a free plugin that edits translations in the browser.
languages/loco/plugins/), which lives outside the plugin folder so updates never touch it.Fixed labels are translated per site language, but the text you type yourself needs a translation per language on a multilingual site. Elevated Product Search registers these strings with WPML and Polylang automatically when you save your settings:
Translate them in WPML › String Translation or Languages › Translations (Polylang), under the context Elevated Product Search.
Two kinds of text follow two paths. Every fixed label in the plugin (buttons, settings, storefront text) is a gettext string in the elevated-product-search text domain: the shipped Spanish covers all of them, and Loco Translate edits them per language. The text you type yourself is stored with the settings and registered with WPML and Polylang as you save, so multilingual sites can serve a version per language without touching the original.
The plugin is still in English after switching the site language. Your user profile language overrides the site language in the admin. Check Users › Profile › Language.
A string is missing from WPML or Polylang’s translation list. Strings register when they are saved: re-save your settings and the string appears.
Loco translations disappeared after a plugin update. They were saved in the Author location, inside the plugin folder, which updates overwrite. In Loco Translate, use Move to relocate the file to the Custom location (languages/loco/plugins/).