First, head to my.otus.com, and click the Google button.
Enter your Google email address, then click Next.
Enter your password, and click Next.
The first time you log in, you'll have to allow Otus to access certain data stored in Google. Click Allow to continue.
You're now logged into Otus with Google SSO! If you're already logged into Google when you attempt this, you'll skip the email and password steps, and just have to click on the email you wish to sign in with.