Upgrade from 14.04 to 16.04

how can I upgrade? the software upgrader does not offer the upgrade even though I have checked upgrade to LTS should be offered. it upgrades the kernel and the linux image, but the desktop stays the same.
stephen@stephen-AO725:~$ uname -a
Linux stephen-AO725 4.4.0-57-generic #78~14.04.1-Ubuntu SMP Sat Dec 10 00:14:47 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Hi @stephenbbb,

take a look here:

Please verify its 14.04:

lsb_release -a

No LSB modules are available.
Release: 14.04
Codename: trusty

Hi @stephenbbb,

take a look here:

Did you run the following terminal (Ctrl + Alt +t) command as well?:

sudo update-manager -d

First, make sure that your packages are up to date:

sudo apt-get update && sudo apt-get dist-upgrade

Then, try to start the Update Manager like this and check if it tells you that there’s an upgrade available to Ubuntu 16.04:

update-manager -d