First login to your enom account. Go to "Manage Domains". Then click on the domain you would like to setup forwarding for. In order to use Enom's URL forwarding, you must be using their default nameservers. This can be set in the "DNS Server Settings" area. Once you are sure you have Enom's nameservers set, you can then go to "Host Records". From there you can change the Record Type to "URL Redirect" or "URL Frame". You will probably want all of the hostnames redirecting to your site for now. The hostnames currently there should be www, @, and * which is a wild card.
URL Redirect:
This will redirect people from YourDomain.com to Your.long.domain.com. Using this causes your long freebie domain to appear in the address bar.
URL Frame:
This feature will redirect people from YourDomain.com to your freebie long sub domain using a frame. The difference with this feature is that your long sub domain will not show up in the address bar. What happens here is when the user types in your domain, a web page loads with a frame in it. The long sub domain loads within that frame so that users wont notice they are being redirected to a freebie domain.
While URL redirection might sound like a great idea, there are many disadvantages that go along with it. For one, it is very unprofessional for those who are starting a business online. Users dont like seeing that they are being redirected to a freebie host. Even if you use the frame, experienced web browsers will be able to still know they are being redirected. Also remember that your registered domain name will probably not get a very good ranking on search engines since there isnt any real content on the domain.
So with that said, URL redirection may be good for personal use. But if you are starting an online business, you might want to look into getting some web hosting for your domain name. It is a small investment that will give you better results in the end.