Either..
Go to Play Store, search for Kodi and install like any other app.
or..
Using the web browser on the M3 go to the Kodi download page (http://kodi.tv/download/) and select the Android ARM apk. Once it's downloaded find the apk file in the M3 file browser and select it. You'll get the app install screen exactly the same as if you'd installed any app from Play Store.