Where do you find the MAC address on a smartphone?

In order to access Hotspot provided by your internet provider you may have to register your phones with the service provider. You will also require your userid and password. The provider would ask for the MAC (Machine Access Control) address of your phone. MAC address is also called Physical Address. Normally this is found in the settings of your phone.

For Windows Phone Microsoft Lumia 950 it is found under:
Settings---About---Device Information--MAC ADDRESS
With the following format:
Mac Address: 33-F3-8D-99-0A-99 (some fictitious address)

For Apple iPhone 6S it is found under:
Settings-----General----About---;Wi-Fi address
with the format similar to the above.
Wi-Fi address: 33:F3:8D:99:0A:99 (some fictitious address)

You better don't give away your MAC address to anybody as it is unique for a phone. If somebody spoofs it and commits something inappropriate you could be blamed for it.

What is a .nar file?

NAR extension refers to Nikon Capture Advanced Raw file.

You might have found it in the pictures you might have recently captured and saved to your Camera Roll. Perhaps you might not have associated these (.nar files) with the cute effect you might have observed. You click on one of these images and it comes to life briefly (Live Images)  before settling to a still that you have been used to all along. These are live pictures.

If you try to attach it with a message you will get two options, an image or a video. I sent it out to my wife to her iPhone 6S and she got a video. The video effect on iPhone 6S is Ok but not like it is on Windows 10 Phone Lumia 950. You have got to see it to know how it looks. This is developing area  of  rich capture.

Read all about it here:
http://allaboutwindowsphone.com/news/item/21078_Rich_Capture_finally_fixed_for.php

How is this done?
Briefly, a number of shots are taken successively and combined smartly to produce a file that produces this effect. The same idea is extended to provide a better illumination for the captured object than in the original.