Upgrading firmware is one of the easiest things in Unleashed. After you login to Master AP's UI - which represents the entire network you can initiate the upgrade for all the the APs that are part of that Unleashed network. Go to 'Admin & Services->Administer->Upgrade' and the click 'Upgrade' button on your right.
By default, "online upgrade" is selected which means that your Unleashed network needs to have internet connectivity to pull the firmware you want to upgrade to.
thanks
Nat