formatting powerpoint slide with master page

"On the home ribbon, in the Slides group, click the Layout button, then select a layout from one of your existing slide master styles to replace the one it has brought with it.

If you are pasting a new slide in slide sorter view, when it pastes you get the little clipboard icon to give you paste options where you can choose to keep the original style or adopt the one from the target presentation, so you can do it there easily too."