First you have to buy a krinkov kit, depending on the caliber of the kit you purchase, you select a receiver in 7.62x39 or 5.45x39. My personal choice is Ohio Ordnance, or if you have some skills of the do it yourselfer, you could buy a receiver flat that you can complete yourself. This is not a route you want to take if you do not have the skill or the tools. Lastly you must decide if you want to assemble it yourself or have a professional do it. You can either do a pistol with no stock or a rifle with a barrel extension in the shape of a silencer and retain your folding stock.
Or you can find someone that has prebuilt Krinks available for sale and buy it ready to roll.