The HPE IMC WSM (Wireless Service Manager) module is required to manage Wireless Fat/Fit APs solutions. I'm not expert in Aruba Instant management through IMC but a matrix of supported wireless devices vendors/models (APs and Controllers) can be found for sure on HPE IMC 7.3 WSM module E0506P02 Patch Release Notes (September 2018) which should be installed and licensed on latest HPE IMC 7.3 E0605P06 platform (November 2018 if I recall correctly).