After making changes within the item's style, layout, text, or read more, under the heading 'Apply to all similar' check either 'On this page' or 'On all pages' & click done. This will apply changes to widget which are assigned to look the same, either on the same page or on the whole website.
Note: If you make style changes and quit the widget it will not be assigned to the other widgets anymore.
Don't make that mistake! because then you will have to assign the widget to look like the others again if you still want to apply mass changes.