To finish the process of using his new computer, Quinton will need to install an operating system (OS) as the primary software that enables him to interact with the hardware and manage files and programs. After installing the operating system, he may also need to install additional software applications (such as web browsers, productivity tools, or games) and drivers to ensure that all connected hardware components (like the printer, graphics card, etc.) function properly.
So, the correct answer is software—specifically, he should focus on the operating system and any necessary drivers and applications.