When working with the Hornbill API's, you'll need to know where you'll be targeting the API calls. This article explains how to identify the API endpoint relevant to your instance.
How to Find your API Endpoint
1) Login to Hornbill Administration via https://admin.hornbill.com/[instanceName]/
Hornbill Web Services API Documentation
Once you have found your instance endpoint following the steps described above, clicking on the endpoint link will take you to the Hornbill API documentation relevant to your instance i.e. relevant to the applications you currently have installed. The general Hornbill API documentation that can be found via a web search will show all Hornbill API's including those in development and for the entire range of Hornbill apps.