Extra amount to the cost of real time shipping method

Log in your administrator panel and open the Shipping methods page (the link to this page is in the SHIPPINGS/ TAXES side box on the left of the page).
Click on the Edit link of the desired real time shipping method.
Enter the desired rates in the Shipping charges section and click on the Update button. These rates will be added to the shipping cost which will be transferred from the website of a real time shipping service (for instance UPS, USPS etc.)