how to create subdomain.

hi.i need to know how to creating subdomain into my domain.My domain is http://www.ptm.org.my and i want to create another server with this name http://ptmit0001.ptm.org.my.so how do i start first.thank you very much for your ideas.

ptmit0001 is my pc that using this DHCP ip 192.168.10.10.