Integrating any review apps to your Google Ads is done by Google themselves. If the review app is approved by Google, it would be integrated with LimeSpot Ads automatically. Learn how Product Ratings work and how to integrate with them with this help article from the Google Help Center.
Google is already partners with a few review apps. Go here to see the list of partnered review apps.
Some review apps that are in our partner network and also integrated with Google include:
Okendo
Yotpo
If your review app is not listed in the above link, the easiest way to add your review ratings to the Google Ads is by uploading your reviews feed which is available from your review app. Learn how to upload your reviews feed from this Google help article.