How to upgrade Drive PX 2 from buntu 15.04 to 16.04?

The OS running on my Drive PX 2 is ubuntu 15.04 (cat /etc/lsb-release).
How to upgrade to 16.04?

Am I supposed to get an account from to download some files?
But that page does not have an entrance to register an account?
Where can I get an account for that site?

Hello Jishao,
Yes, you need to get an account to access the site.
Could you please contact your local NVIDIA team? Thanks.