Need help to install Lollipop on HTC M8 AT&T

I have HTC M8 AT&T running on Android 4.4 KitKat, the problem is that I cant receive any software update because I am not currently in the US. Each time i press on get software updates it says I have the latest version.

I want to install the Latest Android Lollipop and Sense 7. How can I do that. Please help.