I want to download it on my mobile.
What Android version is currently installed in your mobile phone? Because the LINE application supports 2.1 and higher versions. If you already have 2.1 and higher, then you can easily install it in your mobile from Google Play.
You can download and install LINE: Free Calls & Messages from Google Play store. For that you need to have an Google account and Android OS 2.1 or higher installed on your mobile.