When it comes to your checkout page with the checkbox to make the shipping the same as the billing eCart does this for you automatically. If you run the wizard and specify on the first page that you will be offering shipping service then the checkout form that is generated will have this checkbox to make the shipping the same as the billing.
If you wanted to after the fact you could use CSS Form builder on this form to modify or edit it. I hope this clears up some confusion on how you could accomplish this. Please post back if you have any further questions.