The curl command is a versatile tool for working with web sites and web applications.

Invoke curl a second time and post the login data. Now invoke curl a third time passing the URL of the actual page that you want to retrieve. If the site has a logout link you can optionally also use ...

Here is how you can install CURL on Windows systems. It is preinstalled, or you can download it separately and add it to the path, and use it from anywhere.