Dark ground

Hello everyone. I was wondering if I could trouble someone to help me with another question I have about oil painting. I currently use a pre-primed white canvas and then stretch it on wooden bars. I would like to experiment with different colour grounds. Can I apply a dark ground to a pre-primed canvas and if so, how do I do it? Or is it necessary to apply the ground in the priming? I am a little confused.

Thank you for your help in advance. I hope one day to be able to offer advice myself.

Yours ever,
Arthur Banks