It depends if you apply while in the US or not.
(a) Outside the United States:
Apply at the U.S. consulate of your place of nationality. Application is done through the DOS Online Visa Application. See link for details on what the process of applying for a visa entails: https://travel.state.gov/content/visas/en/employment/treaty.html.
(b) Inside the United States:
You must be in lawful nonimmigrant status. For more detailed instructions on filing with the USCIS, the link is:
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