The marriage must be legally possible according to laws of the state in the United States where the marriage will take place. The marriage must be concluded within 90 days of the visa applicant’s admission into the United States , otherwise the alien must leave the US .

The consular officer will notify the beneficiary when the approved petition is received from the National Visa Center and provide the beneficiary with the necessary forms and instructions to apply for a K1 visa.  A fiancé(e) visa applicant is an intending immigrant and, therefore, must meet documentary requirements similar to the requirements of an immigrant visa applicant.  The following are normally required:  

• Valid passport;
• Birth certificate;
• Two Non-immigrant visa applications [a form DS-156, prepared in duplicate]. You must fill out the form DS-156 electronically and print it out;
• One Non-immigrant Fiancé(e) visa application (Form DS-156K );
• Divorce or death decree of previous spouse;
• Police certificate from all places lived since age 16;
• Medical examination;
• Evidence of support (a Form I-134 may be required);
• Evidence of valid relationship with petitioner;
• Two passport style photographs (See photo requirements )
• $131 payable in dollars or Rupiah at the time of the interview.
  

After the marriage, you spouse must file Form I-485 (Application to Register Permanent Residence or Adjust Status) with the USCIS office that serves the area where you live.  The US citizen petitioner must also fill out the Affidavit of Support (Form I-864) with USCIS for the application to become a Legal Permanent Resident.

For further information, please check www.uscis.gov, especially the section “How do I bring my Fiancé(e) to the US” and Frequently Asked Questions (FAQs).