Erp hosting server ip convert to DNS

Hello Good Morning to All,

I have CentOS Server installed ERPnext Successfully up and running. i have one static ip and also forwaded port no. 80 from my router. i can able to access erp over internet from anywhere which is hosted in my office. in URL am using my static ip/login ex :;- .0.0.0.0/login i cannot give my static ip to everyone. now i need to change into erp.mydomain.com even i have achieved this too by editing host file.
now is there any way to access directly erp.mydomain.com without editing host file or any entries in host file.

Better to find solutions on Google?
You can start here http://www.webhostingtalk.com/showthread.php?t=666006