Preparation of the I-129F visa application
First you and your fiance need to assemble all the information that establishes your relationship. This includes, email correspondence, love letters, phone records, and plane tickets of trips to see each other. Photos of both of you in different locations are very helpful.
Interview at the US Consulate abroad
After the I-129F petition has been submitted to USCIS and approved, then the fiance will have an interview at the US consulate abroad. The consular officers may ask questions about the relationship and other evidence provided. The officer can then stamp a visa in the passport and the fiance will have to marry the US citizen within 90 days of entering the United States.
Entry to the United States
The fiance will then be allowed to enter the United States after the visa has been stamped in the fiance's passport. After entering the United States, the couple will need to get married within 90 days. This is very strict requirement and it must take place within the specified time period. After the marriage ceremony the couple can then apply for a green card.