You can add a new domain to the multiple domains Linux Shared Hosting plan through the Add-on Domain feature of cPanel.
To add a new domain,
- Log in to your cPanel account.
- Click on the Addon domain icon and add a new domain.
You can refer to our Knowledgebase article for detailed guidance -
https://manage.accuwebhosting.com/knowledgebase/1993/How-to-create-an-addon-domain-in-cPanel.html