When buying your board, your local retailer will talk you through all you need to know about setting up your board.
But if you're still stuck: There are different ways to set up your board, and also different trends - wide and duck footed, skinny and straight footed. But the main thing is to ride what is comfortable to you.
The easiest way to do this is lay your board down on the ground without bindings. Stand on your board somewhere between the binding threads and see what is comfortable for you and adjust from there.