There is the New Domain wizard located in the Wizards node of the IceWarp Server console where you can quickly add a domain whose setting you can modify at a later stage.
Double-click the New Domain icon to start the wizard.

Type the Name of the new domain, a fill in the Description field and press Next.

Select the Domain Type from the drop-down list.

Specify a Domain value, dependant on the Domain type (see the Domains Domain section), and press Next.

Enter an Email address of the domain administrator and press Next.

Check your settings and press Next.

Check the screen for any error messages. If the above screen is shown, then your domain has been created successfully!