There are four levels of certification, A-D. You can apply for the level you want and have the most experience in. You do not have to start at the most restricted level and work your way up. See the Certification Levels Summary Chart for a description of levels.
To become certified as a well contractor, submit an application for the desired level. The purpose of the application is to verify you have met the experience requirements for the level sought. Once the application is approved you will be notified by mail. For level A applicants, the next step is a field observation.
The final step for all levels is to take the written examination. The written examination is closed-book.