Few other things I can suggest:

There is good information at http://nepal.usembassy.gov/

First step is to fill applicaitons form and file application at Nabil bank, pay fees and get an interview date. Normally only photo copies of documents need to submitted during application and the Originals should be taken during the interview.

During interview, F1/F2 visa applicants may need to show ties to home country.
Upon visa approval additional fees may need to be paid.