The Pingdom Help Centre here at https://help.pingdom.com is our official documentation on how to actually do things with Pingdom.
Other than that though it's also possible to sign in and view tickets you've had with Pingdom Support or raise new tickets.
To sign in simply click the sign in button.
Now comes the peculiar bit, if you've had contact with Pingdom support you have an account registered already but you do not have a password. Simply click the "get a password" link and you'll have an email with a password reset link within minutes.
With that you're then able to log in and see your ticket history!