An email alias is an alternative name for your email account. To create an alias for your emails, open the Emails → domain name page and scroll down to the Manage Email Accounts section.
Once there, click on the Options (⋮) button in front of the email account in question:
And choose Create Alias:
Enter the alias for the email account in the pop-up window and click Create:
You will also be able to see and manage all the email aliases on the Email Alias section:
That's it! From now on, all messages sent to the alias will be forwarded to the email address you specified.
If you're using Titan Email, you can create an email alias following this guide: How to set up an email alias for Titan Email?