Licenses are good for a term of 10 years.  You can renew your licene online, cost-free, by going to the FCC web site up to 90 days prior to the expiration date:   The current URL for this is:  https://www.fcc.gov/wireless/bureau-divisions/mobility-division/amateur-radio-service, but there is a good chance that will change before you need to renew.   When it's time, just go to the FCC web site and look around.    Or check the ARRL's web site for the current instructions.