So ...

Upon activation, go to Settings => Link Checker. As you access the page, the plugin will automatically start looking for broken links on your website in the background.

Depending on how much content you already have on your website, it could take some time to go through all your posts and pages and to display the results. So be patient ... Wait till you'll see the "No URLs in the work queue" message next to the Status info ...

Finally, you'll see the number of broken links and a link that will allow you to see all the affected (broken) links:

As you can see above, you can define a scanning frequency and you can "request" an automatic email notification too ...

OK. Now let's see the final step ...