To setup a domain redirect you need to login to the client area, then click on Domains -> My Domains
You will see the list of your domains, click on the one you want to setup the redirect
And click on "DNS Management"
You need to setup 3 records, selecting "url redirect" from the dropdown as in the following image:
As soon as you edit this records the system will set the nameservers to our default values:
You will have to wait a few hours until your redirect will be working.