What is a Reliable/acceptable Website for Someone to Become an Officiate?

We live in Texas and are wanting to have a friend officiate our wedding, we are struggling in finding good resources for him to become an officiant. Technically, the officiant doesn’t have to register with the state but we are looking for a legitimate website or certification for him to go through. I don’t want years later to find out our marriage isn’t legal because of XYZ. I may be paranoid but does anyone know anything about this?