The USTA is the governing body for tennis in the United States. It is a member of the International Tennis Federation (ITF), which is the ultimate governing body for tennis worldwide. The USTA is comprised of 17 Sections, each representing one or more states. Some of these sections have created Districts that represent specific geographic areas within the Section. Some umpire associations may require an annual fee while others have automatic membership without fees. All certified tennis officials must be members of the USTA. No additional membership fee is required to belong to the National USTA Officials Council, of which you will become a member once you are certified. Your USTA section might have an officials council you would need to join and a membership fee could be involved but these organizations vary from section to section.
To become certified umpire, individuals must attend an annual training course and pass an annual written test appropriate to the type of officiating you plan to pursue. The Sectional or District contact person (you can find the list of Sectional Chairman with contact information here) can tell you when training courses will be held throughout the year. The entry-level official is termed a Provisional Umpire. You will want to be certified as a Provisional Official as soon as possible. Provisional Umpire is the only certification that does not require prior attendance at a USTA training course. To become a Provisional Umpire, you must be a USTA member, pass the Provisional Umpire’s test (which can be found here) , pass a criminal back ground check, and attend the training session in your area.