Your computer should be able to use generic drivers it already has to run the video card at a basic level. The nVidia drivers should be loaded however to give you increased stability, functionality, and speed.
You can go to the nVidia website and download drivers directly from them. It is easiest if you do this first and store them on a flash drive to load after installing the video card.
You can find detailed, step by step insturctions for installing a video card at this web page, including directions about loading drivers:
Rocky, why would you need to d/l the drivers to a flash drive? Nvidia site makes it easy to automatically d/l and install the drivers in one 'swell foop'.
I assume you mean installing the drivers after starting up with the new video card, having thus already installed the generic driver. I find it simpler and cleaner to have the drivers on hand to install when queried by the "New Hardware Found" window during installation. No old driver to worry about. The system handles it. But I do not profess to being an expert on driver installation so if you think that method is better please enlighten us.