Hi
You don't need to setup anything special on the Aruba for using Iperf.
What you need is two computers, both running Iperf.
How you can set it up, you can find here: https://iperf.fr/
Iperf can be used as both a client and server, this way you can measure speed to and from a site. Or you can setup 2 tests at the same time, to simulate traffic both ways.
Roar Fossen