The three ways by which a new employee can be added to the HR system are Add Pending Worker, Hire Employee, and Convert Pending Worker. Adding a pending worker allows future employees to be entered into the system before their official start date. Hiring an employee is the standard method for adding new hires directly into the system. Converting a pending worker involves changing the status of a previously entered pending worker to an active employee. Mass Upload Employees refers to adding multiple employees, not a single new one, and Employee Self Register isn't typically a main HR-driven method.