You can update all the DNS records form the client area, the Cname, A records, MX records, TXT records and all.

The process of there DNS update bellow is correct but it is not available now and you can try this to update from your cpanel  http://www.luvbeingworld.com/knowledgebase/134/How-to-Update-DNS-Records-from-Cpanel.html

To update Cname records, bellow is the steps,  
Click on Domain taps >  My Domains >>  Tick the box to select any Domain you want to add the records to >>>  Scroll down ward to have WITH SELECTED, click to have option menu, choose Manage Domain or option at the edge of the domain strip >>>>  By the right you have options under manage >>>>>  DNS Management >>>>>>

You have columns for Host Name, Record Type, Address and Priority. Fill the required Host Name, sekect Record Type to select any record you want to add, egg Cname, AAAA records, MXE records, MX records TXT record and any record you have.

You can do the repeatedly of you have multiple records to update.