In RepU, open your widget and click Copy next to the embed snippet.
In Squarespace, open Pages, scroll to the bottom, and choose Custom Code, then Code Injection. Paste your code into the Footer box.
Click Save, then open your live site to see your Google reviews.
Check your live site in a private window, not the Squarespace editor. A domain-locked widget only shows on your own domain.
Code Injection needs a Core plan or higher. If you are on Basic, upgrade, then check again.