Install Reviews extension

For OpenCart 3.0. Five steps, all in your OpenCart admin. You need the zip from your purchase email or from Your software.

Step by step

Upload the zip

In your OpenCart admin, open Extensions, then Installer. Press Upload and choose the zip you downloaded.
Install it

Open Extensions, then Extensions, and choose Modules from the drop-down. Find "Reviews from Amazon, eBay and more", press the green +, then the blue pencil.
Choose how reviews show

Set Status to Enabled. Pick Where reviews show (Automatic suits most shops) and Reviews on the product page, then press Save.
Add your scores

Open Catalog, then Products, edit a product and open its Reviews elsewhere tab. Press Add a place and enter the link, the real overall score and the number of ratings, as that page shows them. Press Add a review for any reviews you want to quote, then save the product. To do many at once, use Bring in reviews from a file in the settings.
Check your shop

Open a product you added scores to in a private window, on a phone and on a computer.