There is an entire process involved and would require you to file an Immigrant Petition (I-130) and process an Immigrant Visa Application with the National Visa Center. The USCIS website has an excellent overview of the process. See: http://www.uscis.gov/family/family-us-citizens/spouse/bringing-spouses-live-united-states-permanent-residents. Alternatively, you could engage a Law Firm to take care of the paperwork.