It's not called park a domain in DirectAdmin, the option that most resembles what cPanel calls a parked domain would be a domain pointer. Note though that with a pointer it will duplicate what the domain it points to have as settings. You will not be able to configure the domain itself in any way (including adding email accounts).
Depending on your aim, it may be better to add it as a separate domain through the account portal, as this option gives you all benefits of having your custom domain such as being able to control DNS and create email accounts on it.