You can log in via social media or via your email. As an administrator you have to remember to log in with the same email address that you are registered with on the user administration site on the platform. This is most likely your work email.
Google: If you have a Google account, and wish to sign up with this one, you just click on the red Google icon, and you will be logged in automatically.
Email address: If you don't want to sign up with a social media account, but want to have a separate account, simply write your email address in the empty box under the icons, and click on the arrow (see below).
Facebook: Just click on the Facebook icon and you will be signed up automatically. This means you do not have to make a new password. If you choose this option, your profile photo will be added to your profile automatically.
2 Factor Authentication
When you log in to your dashboard the first time, you will be asked to register for 2 factor authentication. This is to add an extra layer of security to your page. You can read more about this here.