Sizing footer widgets in ThemeForest - Ace

A WordPress learner here wanting to be able to size the ‘box’ in which the widget footers are located. I am pretty sure that I have to go into the editor yet I am not sure which Template to use. I tried to change the style.css yet there was no difference in any changes, e.g., color, padding from 24 to 12, that I made. Thanks for any help you may provide.