When using the automated scan option with OWASP Zap, you supply the URL to attack. This will spider and attack the provided URL, based on selected options.
But, this is often the login page. Given known credentials, how do I log in and then continue scanning (preferably, either by a one-click to Automated Scan button or via command line Full scan)?
You need to configure ZAP to understand your applications authentication. The easiest way to do this is via the ZAP desktop even if you want to use it in automation - its much easier to test in the desktop and then you can export the context which you can import when automating ZAP. There are lots of videos about this - search for the 'authentication' tag on https://www.zaproxy.org/videos-list/
