There are several ways to install ClipCoverage.
Direct Chrome Web Store link:
https://chrome.google.com/webstore/detail/clipcoverage/iijconbojdgdnkjeoamnflldidgenjde
Direct G Suite Marketplace link:
https://gsuite.google.com/marketplace/app/clipcoverage/485482013710
Install via clipcoverage.com:
Login to ClipCoverage, and click Install now in Quickstart guide:
Search from Slides add-on store:
Open a Google Slides file > Add-ons > Get add-ons..., and then search "clipcoverage".
