In the states I've lived in, the state DMV office sends a renewal notice (online or by mail) before the expiration date in order to renew.
Alternatively, I now live in a state where I have an account online with the state govt for issues just like this one - my car, voting, etc. so I can go in and renew that way.
If I were you, i would go onto your state's website and search under vehicle registration and likely you will find directions there.
When we give up the need to be special, life becomes special.
Inappropriate and offensive post removed.