Share contents between my Galaxy Note 5 and Samsung Smart TV
Screen mirroring is a feature available on some editions of Samunng Smartphones, but unfortunately has been removed in later builds on smartphones and replaced  Samsung Smart View and related.


  Using the Screen Mirroring feature, you can share your Galaxy device’s
  screen with your Samsung Smart TV or with an HDTV using the AllShare
  Cast Wireless Hub.


The following phones support the Screen Mirroring feature by default. Some phones can be modified through a custom ROM, so they also may be able to support screen mirroring.


Samsung Galaxy S3, S4 ,S5                                 
Samsung Galaxy Note 2, 3, 4 


Nevertheless you can use alternatives app to achieve the same e.g Screen Mirroring from Playstore.

Another aggressive way of enabling the feature in Note 5 is perhaps rooting and editing build.prop line: wlan.wfd.hdcp=disable (anywhere within the additional build properties section, preferably at the end)
under /Device/system folder. (Remember to save and reboot) as outlined here on XDA thread.