You have added a site, discovery has found your pages, and you have chosen which ones to scan. Starting the scan is the easy part.
Start it
Open the website and choose Scan. That is the whole action. You do not need to stay on the page, and closing the tab will not stop it.
While it runs
The automated checks run against each page you selected. The website's entry shows its progress, and the Dashboard shows scans in progress across your whole workspace.
When it finishes
The scan shows Automated Scan Complete and your results are ready to use: every issue found, on every page, and a report you can download.
There is no score at this point. This is the single most common source of confusion for new customers, so it is worth saying plainly: a scan with no score is not a broken scan. A score comes from an Expert Manual Review, which you request. There is a whole article on this, linked below.
If a scan fails
Occasionally a scan cannot finish, usually because the site became unreachable partway through or something on the network blocked it. Individual pages that cannot be loaded are marked as failed and the rest of the scan carries on. If a whole scan fails, or fails repeatedly, check that the site is reachable and that nothing is blocking automated visitors, then contact support.
Deleting a scan
You can delete a scan you no longer want. This removes its result and its report, so download anything worth keeping first.