I checked your account, but there are no domain names on it right now. The “Parked Domains” feature can be used to create an alias for one domain to another domain which is already on the account. So if your account doesn’t have any domains yet, you cannot add any parked domains.
The solution is simple: just add the domain through the Addon Domains instead.
I’m sorry, but why do you keep focusing so much on the parked domains? There is no difference between an addon domain and a parked domain, except for the website folder they are assigned to.
What exactly do you believe adding your domain as a Parked Domain is necessary for?
The domain is currently in use on unaux.com. Please login to your hosting account at https://cpanel.unaux.com and remove the domain name from there.