There are two basic steps to applying for a fiance visa or K1 visa:
Step 1: Fiance visa petition
The fiance visa petition process begins when a United States citizen submits a Form I-129F fiance visa petition on behalf of their fiance. This petition requests that your fiance be allowed to enter the United States so that you can get married. You will need to wait for your petition to be approved before you can move on to the consular processing stage.
Step 2: Consular processing
The consular processing stage begins after the fiance visa petition is approved and the petition package is forwarded to the National Visa Center. The package will stay at the National Visa Center for a short time before being forwarded on to the embassy. The embassy will then contact you with information on how to schedule your fiance visa interview. During this stage you will need to submit the fiance visa application along with the supporting documents such as a medical exam report and police certificates. Assuming that all goes well at the interview, your fiance will be issued a fiance visa and will be able to join you in the United States so that you can get married.
A final step that is not part of the actual fiance visa process involves the application to get a green card after you get married:
Step 3: Adjustment of status / green card application
After you get married, your new spouse will need to submit an application to do what is called “adjustment of status“. This is the process that allows your spouse to get permanent resident status and a green card. After your spouse submits the adjustment of status application, they will normally be scheduled for an interview. If all goes well at the interview, they’ll get their green card in the mail shortly after the interview. The green card will be a “conditional green card” which means that in two years you’ll need to file a separate application to remove the conditions on the green card.