Hello,
If I am assuming that the APs are running in autonomous mode:
In the main menu of the AP GUI go to VSC (Virtual Service Communities). You should see a list of all configured SSIDs. Klick on the name of the SSID you want to disable. A menu with the title Add/Edit Virtual Service Community will be opened. In this menu search for the sub-menu "Virtual AP" and remove the checkmark from the check box, This will disable the SSID.
If you want to remove the SSID configuration completely at the botton of the menu there should be a delete button,
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-c04514136&withFrame
In controlled mode it is slighly different because here you have the concept of AP groups and more steps may be needed. I will not go into detail but I think disabling the Virtual AP will do the same.