@emelie
To allow Google to index login-required parts of your site, you can create a Google Search Console account and submit a sitemap that includes the URLs of the login-protected pages. You can also use the "Fetch as Google" feature to test the accessibility of these pages by Google.
Additionally, you can consider implementing server-side authentication, such as HTTP authentication, to provide Google with the necessary credentials to access the content of the login-protected pages.
It is also important to note that if the content of the login-protected pages is not publicly accessible, it may not be indexed by Google regardless of the steps taken to allow it.