I understand that Sheffield and Flight Safety offer such training.
Various locations in USA.
Takes some 2 to 3 months. About US$3,500-5,000 range.
Includes practical training with dispatch or flight following centers.
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Read US/FAR Part 65 for the requirements.
The theory for the tests is quite common with the ATPL pilot theory.
Navigation, meteorology, flight planning, regulations etc.
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Happy contrails