The Salesforce Interface
The Best way to Get Familiar with Salesforce is by reading the basics in Trailhead.
Salesforce comes in two flavors:
Salesforce Classic -- the older version of Salesforce still used by many long-time HandsOn Connect customers.
Salesforce Lightning - the modern interface for Salesforce, which is automatically setup for new Salesforce users. Classic Salesforce users are being increasingly 'urged' by Salesforce to switch over and start using the Lightning interface.
In the App Selector in Salesforce Lightning you'll select the app "HOC Lightning". It has all the objects (tabs) used by handsOn Connect, a HOC home page, and all the necessary 'quick actions' for using HandsOn Connect.
To learn about getting around in Salesforce Lightning - please read this article from Trailhead: