You have to file Form I-140, Immigrant Petition for Alien Worker with the USCIS. Normally, a US employer will file this petition to sponsor an employee, but immigrants applying for a National Interest Waiver can apply on their own.
Along with the petition, you will also have to include extensive supporting documentation of your eligibility for a National Interest Waiver. Ensure that your evidence is in an easy-to-understand manner that substantiates why you qualify for the National Interest Waiver.
The petition should also include a letter addressed to USCIS that provides a summary of your case. It should include:
a description of your field and your area of expertise.
a description of your work and how it affects the field, including a discussion of your work’s current and future applications and an explanation of how this work is in the national interest of the US.
an explanation of why someone with your high level of skill is required to perform the job that you intend to perform in the US. You should have supporting evidence to back up the statements you make in this letter.
You can include the statement you wrote about your work, your field, and your exceptional ability in the petition cover letter. If you do have a job offer in the US, provide details about your future employer. You should also provide a detailed description of the specific job you will perform in the US.
You have to be systematic and thorough when writing the petition cover letter. The letter should be written in simple English. The USCIS officer who is deciding your case cannot determine that you qualify for a National Interest Waiver unless he/she can understand what you do. So your petition cover letter should be easy to read, informative, and convincing.
Consular Processing (If you are applying from outside of the US)
After your petition is approved by USCIS, they will forward it to the National Visa Center, which processes all immigrant visas for applicants living abroad. The National Visa Center will issue an immigrant visa packet to you containing instructions on how to apply for your visa at a US consulate abroad.
You and any accompanying family members will need to get the required medical examinations and police clearances as described in the immigrant visa packet. You should also appear for an interview at a US consulate. At this interview, a consular officer will decide if you are eligible to receive an immigrant visa. The officer may ask you to describe your accomplishments and may review the evidence you provided in support of the petition you filed with USCIS. If the officer approves your application, you will receive an immigrant visa in your passport.
The immigrant visa will be valid for six months. Within this six month period, you have to enter the US. When you enter the US, an immigration officer will stamp your passport and you will become a legal permanent resident. The stamp in your passport is valid for one year and you can use it as proof of your status as a permanent resident (green card holder). Within a few months of your entry, you will receive your permanent resident card by mail at your US address.
Adjustment of Status (If you are applying in the US)
You have to file Form I-485, Application to Register Permanent Residence or Adjust Status. You may file this application at the same time as Form I-140 or after Form I-140 has been approved.