Is the rx 6950 supported?
RX 6950 XT supported, check NootRX website

How exactly install this kext?
Hackintosh guide, or if you already have hackintosh on your PC then just copy kext to EFI/OC/Kexts folder and add kext to Config.plist

This is the github of the NootedRed project which is responsible for supporting AMD Vega integrated graphics cards, for discrete graphics cards use NootRX