You are downloading the MX Player APPX file v2015.317.623.5601 for Windows Phone. MX Player is a free and useful Music app: MX Player - The best way to enjoy your movies. This is offical port of MX Player but contains small subset of Android version as it is ... You can now download the offline APPX file to install & try it.
Download Locations for MX Player 2015.317.623.5601 APPX file
Note: To install it manually from an SD card, you should choose one of the server location above to get the offline MX Player APPX file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.