so you have a demo account on Aruba Central. as this is a POC you'll need to add the devices manually to the account and then add/assign licenses to them. You can do this directly from the Central account (under maintenance). there is doc online in Central explaining this (little 'talk' bubble upper right hand corner). enter the HTML doc and search 'adding devices'.
In addition you can register for an Aruba Activate account, enter your devices in activate and create a folder to push these devices to the Central account.