The first step in using Hackystat is going to a Hackystat server and registering with it by providing an email address that you can access in the "Registration" field and pressing "Submit". This results in the server generating a unique 12 character "user key" and emailing it to you. The User Key is used to identify incoming sensor data as having come from you, and also to allow you to login to the server and view your data. You should not share your user key with others.
Section 3.2, “Account Registration” documents the registration process in more detail.