Trying to remove an domain from Office 365 E3

Trying to remove an unused domain from the list of domains in Office 365 (Enterprise).

• I carried out all steps in http://office.microsoft.com/en-us/office365-suite-help/remove-a-domain-HA102818535.aspx
• http://support.microsoft.com/kb/2787210/en-us refers to steps to be carried out in PowerShell. At this point, I am not familiar with PowerShell, and it seems a bit too risky for me to enter this command line interface... But with good guidance I would be able to do it.

I noticed that the only place where I can find the domain is in the list of AcceptedDomains in e-mail flow on the Exchange admin page.

Yet, I don't seem to be able to remove it from there.

Pls advise.