You’ll need to have a Google account, and barwen.ch. If have a gmail address (for example) then you have a Google account. You can sign up for a barwen.ch account on the toolbar at the top of this page.
Go to the barwen.ch front page and click on Log in using your browser.
Sign in to Google using your regular username and password.
A terminal will appear in your browser.
For more technical details, you can read the browser login project page.