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".