Since you have only one AP then just go to Admin & Services > Administer > Upgrade in the Unleashed web adminstration dashboard. The default Online Upgrade option can automatically find the latest firmware release for you, then let you kick off the upgrade. Details are here.
(I have an unofficial tool here which finds the latest compatible firmware, if your Unleashed network has more than one Ruckus AP model, or you want to upgrade manually).
