If you put a stent in my renal arteries, can I keep smoking?

No. Smoking is probably the single worst thing you can do to yourself in terms of peripheral vascular disease.
Not recommended! Your smoking probably contributed to the narrowing of your renal arteries, perhaps significantly. You might want to ask yourself why you would want to continue smoking after having a procedure that is not entirely benign. Smoking is very addictive but there are methods and medicines that can support your through smoking cessation. I hope that you will pursue these with your doctor and quit!