Here we go ..
1. login to wix.com
2. edit your site
3. select the page where the app is installed or create a page and install the app
4. select the circle + add element feature
5. Select search
6. Search for 'Custom Code' then open it.
7. Add custom code to header section, name it 'Customer Reviews' and click apply
custom code
8. Save and publish your site.
9. Test the code by appending ?&review_form=Y and navigate to products in your website if you multi-page enabled.
Example: https://www.leeacupuncture.biz/reviews?&review_form=Y