The one thing to know about PrestaShop
PrestaShop themes expose different hooks. The widget code stays the same, but the module or template position depends on the theme.
Where reviews belong on a PrestaShop site
A full-width carousel works well on the homepage; a grid fits a landing page; and a compact badge can sit near product or store trust information.
Full-width sections suit carousel and grid layouts; narrow areas suit a badge.
Reviews and search results
The widget outputs review schema markup automatically. Whether Google shows a star rating depends on what the reviews are attached to — worth reading before you expect stars, because for a business reviewing itself the answer is usually no.
What does help either way: reviews on the page are content, and a page that answers what customers actually say is a page people stay on.