In Campus Mode, the AP is managed by an Aruba Mobility Controller. The controller typically pushes the firmware to the AP, meaning you download the firmware for the controller rather than the individual AP.
When browsing the download list, you will encounter different release trains. Choosing the right one depends on your specific needs for stability versus new features.
For users with active subscriptions, Aruba Central is the most efficient way to manage firmware. If your AP-505 is onboarded to Central, the system will notify you when a new "Recommended" version is available, allowing you to schedule a one-click update across your entire site. Selecting the Right Firmware Version
For an Instant AP cluster, log into the web interface of the Virtual Controller. Navigate to Maintenance, then click on the Firmware tab. Select the local file you downloaded and click Upgrade. The cluster will perform a rolling reboot to minimize downtime.