How Do You Change Dns On Linux

ok, i am kinda new to dns. i understand the concept somewhat now. but i am getting stuck with the command, im not used to the SSH thing. do you have a how to on how people like me can change our dns settings. i know you already configured it correctly, and the server can ping out to the internet, but i have to use a different DNS server for this customer which is running an application. so if you can change the dns or if you can show me how i can do it i would appreciate. thanks for all your support. i have really made the right choice with your services, but this is something unexpected and my customer is on my case to change the dns right away but i dont know how to in my red hat server. im just not familiar.