The first step to sign up is to click on the "Sign Up" button in top right corner of the page.
This will take you to the user creation page. In the creation page you can continue using an existing Google or GitHub account, or create a new account using an email address.
The final step of the sign up process is to select a user handle which will be used to reference your datasets and apps.
Once you've signed up and logged in you'll see your avatar in the top right corner of the page (replacing the "Sign up" button you clicked on earlier).
Now that you are signed up you can create your first app! You can do this by following the create an app quickstart guide.