Usually you should be using NetworkManager by default (Ubuntu 14.04), just in case you want to be sure, use this command to verify:
dpkg --get-selections | grep network-manager
In case there is some output like:
it is installed, if there is nothing returned, you are probably using a different network managing daemon.
It would be possible that network manager is installed but inactive. Lets check if its running the hard way:
ps aux | grep network-manager
If thats returning something different than itself, you can be sure using the NetworkManager in Ubuntu / Debian.