You can drag and drop library slides to your presentation. 

On the slide thumbnail four boxes to the top right denote the library slide. 

Any changes made to the library slide which is dragged and drop will reflect in your presentation if you have not made a copy of it. 

You can drag and drop library slides in your presentation and then make a copy of it to create your version of slide. 

When you drag and drop slides from a library presentation to your presentation, you will get an option to get all the linked slides or only that particular slide.

Check the steps below to add library slides to your presentation.