We're going to need more info. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.
Can you elaborate on why you need to upgrade your graphics card? What are you intending to tax your graphics card with? Including a budget for your graphics card upgrade would help us two fold as well as your location and your preferred site for purchase.
If you're asking how to remove or introduce a graphics card into your system, you can look through this;
A lot depends on your setup. So like Lutfij asked we will be better equipped to help knowing your equipment.
That being said if this is a desktop or SFF you should use DDU to remove the old GPU's driver before you remove the old GPU.
But were at a crossroads with advice as you could have a Small forum factor "SFF" computer and giving general advice would get you in a pickle if we gave advice in the forum of thinking this is a full size desktop.
Same instructions but you need to apply different restrictions on a SSF computer.