If you have an active support contract log into the Aruba TAC site, go to Software Downloads->ArubaOS->General Availability->Current Releases and find the release you would like to upgrade to. Be sure to download the Release Notes so you understand the upgrade process. Depending on the version the 3200 is currently running you may, or may not, need to do an intermediate upgrade.
Lastly, is your 3200 a "3200" or "3200XM"? The XM version has more memory (1Gig v. 500MB) and is required for the 3200 to run AOS v. 6.2 and above. If you have a "3200" a memory upgrade kit can be purchased from Aruba that makes it a "3200XM".