T-Mobile is rolling out Android Lollipop 5.1 to their Nexus 6 users today. Your phone should automatically check if there is a new version of software available when you hop on WiFi, but if you just can’t wait, hit your settings button, followed by “about phone”, then click “system updates.”
The latest update will enable Google’s new security feature which allows your phone to stay locked, even if the would be criminal wipes your phone. Also included in the update are improved software stability and various bug fixes, which we know Android 5.01 is far from perfect with bugs like random restarts and poor battery life. The file size is 409MB, and as of right now can only be downloaded over WiFi. Download over cellular data will come at a later time. It’s a rather clever way for T-Mobile to limit data downloads even though many of their plans offer unlimited data.