Shopify
Three routes, depending on whether the reviews already exist somewhere else, live in your store, or do not exist yet.
How to add reviews to BigCommerce
The exact steps for BigCommerce, in about five minutes, without a developer.
The short answer
Build a widget, copy one line of code, and paste it into your page. No developer and no theme files.
Step by step
Build the widget and connect your review sources
Choose a layout and match the colours to your site
Copy the embed code
In BigCommerce: open your page editor
Add an HTML block and paste the code
Save and check the live page
Where to put them
Through Script Manager for site-wide placement, or a widget region on a specific template.
Full-width sections suit carousel and grid layouts; narrow columns suit a badge.
Does BigCommerce have reviews built in?
BigCommerce has product reviews built in, with a moderation queue. Store reviews only — nothing from outside.
If your reviews already live on Google or a marketplace, nothing built into a site builder will reach them.
If they do not appear
Check the code is on the page and that changes were published rather than previewed.
The BigCommerce troubleshooting page works through the rest in order.
Questions
Other setup guides
Any website
Whether your reviews already exist somewhere else, live in your store, or do not exist yet — three different answers.
WordPress
The exact steps for WordPress, in about five minutes, without a developer.
Wix
The exact steps for Wix, in about five minutes, without a developer.