By default, SharePoint lists and libraries will use the Information Management Policy defined in the content type of an item. Optionally, you can set a list or library to have its own Information Management Policy that will override any policies defined by a content type.
The following walk-through will show you how to create a new document library and define an Information Management Policy for it.
Due to the shortest duration being one day, you cannot verify the Information Management Policy works as part of the walk-through. If you will have access to a SharePoint server for at least the next 24 hours, you can create or upload a new document into the library and verify it is deleted after the duration period has elapsed.