I don't administer the DNS databases here, so this is mostly guesswork and a little readingon my part BUT...
Look in /etc/named.boot on the machine running the DNS server (called bind or named) and figure out which file contains the information for your particular zone. Look also in any files which are 'include'd in this file. Edit the zone file by adding a new line for your new hostname -> IP mapping. I will not venture to give an example, because I would surely be wrong. Try duplicating a line for some other server, and just changing the relevant parts. Then, restart named (/etc/init.d/bind stop; /etc/init.d/bind start) or (/etc/init.d/bind restart) or (/etc/init.d/bind reload). I can't test it, but the firt is almost certain to work, the second less so, and the third less again. Try 'man named' for more info. You have to be on the DNS server computer to do any of this. Carl