Hi khai,
With newer AP's we do not make a difference between IAP,CAP and RAP. Those new AP's are called UAP's. UAP's can run as a controller managed Campus or Remote AP or as an Instant AP.
For the first two modes (CAP and RAP) you simply need to connect them to a controller.
For the last mode (IAP), you need to install the correct IAP firmware on the UAP. If you use central, this will happen automatically. If you use airWave this will also happen automatically, if the correct firmware is already loaded to AirWave. If you do not have AirWave or Central, you can download the software from support.arubanetworks.com. The correct image would be ArubaInstant_Scorpio. Ths latest available version is this one here:
ArubaInstant_Scorpio_8.5.0.2_71711