There are several different ways to get your green card (permanent residency) through your job or an offer of a job. These tend to be among the most complicated residency cases and usually involve several different steps.
Step 1. For most employment-based residencies the U.S. employer must file a labor certification application with the U.S. Department of Labor. This is now commonly referred to as PERM. There are however many employment categories that do not need that certification.
Step 2. USCIS must then approve an immigrant visa petition for the person seeking the residency.
Step 3. The State Department must give the applicant an immigrant visa number, this assigns an Immigrant visa to the applicant.
Step 4. If the applicant is already in the United States and in lawful status they may apply to adjust their status to permanent residency. If they are outside the United States they will receive notifications to complete the process through a U.S. consulate.