Configuring a CNAME using the Plesk control panel
To add a cname log into your Plesk control panel – this is provided to you by your website host.
If you are using goddady hosting, see the guide located here or if you are using cpanel use this guide.
Once logged into Plesk select "DNS Settings" on the right.
Select "Add Record".
Select the Record Type as CNAME.
In the "Enter Domain Name", enter the cname you would like. If your site was site.com and you wanted the name stream.site.com enter stream into this field.
In the "Enter a Canonical Name *" field enter the NetroMedia host you would like to mask, for example 155.obj.netromedia.net
Screenshots of this procedure can be found below: