DNS Change - HOW & WHERE!

I need help with this most recent change in Homestead - the DNS situation! I do not know what this means, I do not know how to do it, I do not know where (on your web site) to do it, I do not know by when it needs to be done (or do I just lose all my sites then?)..So how do I to thiis, somebody help this novice (and I'm sure there's millions of us out here)

Woody - CyberPointeDesigns