Product Reviews

For this you would need to install the Shopify Product Reviews app:

Product Reviews - Shopify Apps

Then head here:

  1. Admin

  2. Online Store → Themes → Customise

  3. Navigate to your product pages

  4. From the left-hand menu, scroll to the bottom and toggle the "Enable" checkbox -

WeTheme Help - Enabling Product Reviews on Product Pages

We've already included all the coding required for this app, within your theme's base-code, so no need to add any for it to work.