You must renew your domain on an annual basis. Your best bet is to set up autopay with your domain registrar (for example, Go Daddy), so you don't need to remember to pay it every year.
If your domain has expired, you can notify Flair via our help desk and we can help you determine next steps. However, note that we will not have access to your domain registrar unless we set up your domain for you or you gave us your password.
You can do a WHOIS lookup to determine your domain registrar.