To add a meta keyword, click on the sphere and validate by pressing "Return". You could remove tags by clicking the cross. Increase the indexing within your Prestashop urls in Google. This module AUTOMATICALLY provides, without the need for any manual configuration, the "canonical" and "hreflang" tags within the header https://addons.prestashop.com/en/seo-natural-search-engine-optimization/31857-automatic-google-rich-snippets-json-ld-open-graph-seo.html