This is android only btw.

1. Go to Settings > Security > Turn on ‘Unknown Sources‘ (This step may vary depending on OS ot device but basically you will need to turn on the option that allows you to install non-market apps)

2. Go to your to your downloads and open the app. (usually it shows the recently downloaded app in your notifications center [pull down from top])

3. This screen shown below should pop up, press install.

That’s it! You will now be able to watch free movies on your Android device!