On the ParseHub home page, you can click the menu in the top right and select "Account" to get information about your ParseHub account.
Here, you can find the Account Settings and the Plan & Billing tabs.
The Account Settings tab shows your API key, which you need to use the ParseHub API, as well as your account email, and a link to change your password.
The Plan & Billing tab shows all the limitations and billing information for your ParseHub account.