For this use case, web scraping, you are usually better off using JavaScript in Browser.
I always use a password manager (1Password) to log in to all of my web sites and apps.
It is possible for KM to script 1PW and the macOS Keychain, but let's start simple for now, and add that in after we've got the below working.
Open the web page and log in manually, then run the KM macro.
I can help you with the JavaScript, but I need either the page URL, or all of the HTML code around the section you're trying to control/script. You can use the Chrome Inspector to get this HTML.
Please post the URL, or the HTML using the Forum Code Block.