You can use your additional domain and point it to the root of your primary site. If your primary domain is example.com and point example.net to it and someone accesses example.net, then browser will display example.com.
Login to your DirectAdmin account.
In the
Account Manager
section, click on theDomain Pointers
icon or type “Pointers” in theNavigation Filter
box and then the option will appear. Click on it.In the top right-hand side, click on the
Create Domain Pointers
button.Under “Source Domain”, enter your domain pointer name.
Unmark
Create as an Alias
and then click on theCreate
button.
Your domain pointer will be created but please make sure that your domain pointer nameserver is pointed to the same as your primary nameserver or else it will not work.