If you want to monitor a web app it's probably only accessible after logging in. Login steps allow you to sign into a user account before the page is loaded for analysis.
When creating or editing a page, click "Show Advanced" and then select "Login Step".
From there you can select a login step, or create a new one.
To log into a user account the following information is needed:
After configuring the login step click "Update" to save your page changes.
Click "Test login step" link at the bottom of the login step form. This will log into your site in the background and provide you with debug data like a screenshot and the URL after attempting to log in.
When logging in your web server will most likely set a cookie that's necessary to access the data in the account. When loading a page archive these cookies are restored so that the front-end does not incorrectly think the user is unauthorized.