Answer:
A marriage license is required to have a valid marriage and is usually the first step in getting married is for the couple to apply for a license at the clerk/recorder for their county. This can be done live or online. Then the couple must appear at the clerk's office to pick up the license, or if the couple had applied in person, the license can be sent by mail.
If the license has expired before getting married then you need to get a new one.