By default you have to click the "Start Crawl" button in a project to start a crawl running. When you have a project up and running, you may wish to crawl the site more often. A scheduled crawl allows you to pick a day of the week to crawl the site automatically. You'll get an email when the crawl is done. If you work on problems with your site on a fixed schedule, this is a great way of having data available in time without doing anything.

Within a project you want to choose the "Schedule Crawls" option from the three dots menu at the top right.

Simply choose a day of the week and click Save. If you want to cancel it later, come back and choose "Never".