If you consider Central as a centralized replacement for the Instant local config, you are fully correct. Put the same configuration in Central as you would put in the Instant itself.
To get ClearPass and Instant setup, you may check out the Guest parts of this video series: https://community.arubanetworks.com/t5/Security/Aruba-ClearPass-Workshop-Video-series/td-p/291597
The videos show how to do it directly on Instant, the terminology and options are similar to Central (just looks different).
One change is that with Aruba Central, there will be a certificate pushed to the IAP with the name securelogin.hpe.com, so where the video uses captiveportal-login.arubalab.com (or something similar), put the securelogin.hpe,com there.