Have you added the server behavior to your confirm page already? If so you can then proceed to create the new shipping rule. In the shipping tab of your cart object if you do not see a shipping rule for your UPS you should add one in.
For the trigger of the rule you can use shipping quote > 0, then for the charge you can just use the shipping quote. There should be options in these select lists that directly reference the shipping quote.
Once you have got the rule in place you may need to update the cart display on your confirm page to see the new shipping rule. Please post back with any questions that you have or if you are having any troubles with any part of this.