When first starting it is best to try with you feet at shoulder width or just a bit wider. Make sure your stance is comfortable with your knees straight, but not locked.
Now you will find your natural center or natural point of aim. To do this, look through your scope at the target you are going to shoot. Next, close your eyes and swing back and forth about a foot to each side. Slow down your movement until you eventually stop. You should be on your target. If not, you will adjust your back foot frontward or backward until this is achieved. Over time it will become second nature.