You need to first buy a graphics card and then download the drivers for it from the company site (Nvidia or AMD) not the third party maker like XYZ company.
Or you can let windows update download and install the drivers for a pre existing GPU/iGPU for you by connecting to the net and running windows update.
Or you can try the Laptop manufacturers website to see if there is any update available for the GPU that they have in that specific laptop.
Unless you spent a pretty penny on your laptop in the first place, I doubt you will be able to fit a GFX card to the system. Even if your system has a dedicated card fitted, there is no guarantee that you'll be able to upgrade it due to space/power requirements.