Get a Green Card While Inside the United States
If you are currently in the United States and are one of the specified categories of relatives of a permanent resident, you may be able to become a permanent resident in two steps.
Get a Green Card While Outside the United States
If you are currently outside the United States and are one of the specified eligible categories of relatives of a permanent resident, you can become a permanent resident through consular processing. Consular processing is when we work with the U.S. Department of State to issue a visa on an approved Form I-130 petition when a visa is available. In this process the Department of State will issue you a visa. If approved, you may then travel on the visa and will officially become a permanent resident when admitted at a U.S. port of entry.
Things to keep in mind:
Source: United States Citizenship and Immigration Services (USCIS)