Hello,
I have found the following site to be the easiest to download firmware/software for any ArubaOS-Switch or HPE prodcuts.
https://h10145.www1.hpe.com/downloads/ProductsList.aspx
Just enter the product number or description, and it will take you directly to the webpage of software download.
In addition, for documentation related information on each Aruba Switch, please, visit the following site.
http://h17007.www1.hpe.com/us/en/networking/library/index.aspx#.WxgMhFMvyL4
Thank You,