Make sure you have a current and valid Nigerian passport. The passport should be valid for at least several months after your planned departure from Iran. Foreign ministries are often unwilling to issue visas to persons whose passports may expire while overseas.
Contact your nearest Iranian embassy or consulate for a visa application. The visa application is several pages long, and requests information such as your purpose in visiting Iran, the planned length of your stay and the names of other countries where you have previously visited or lived.
You will need to submit multiple passport photos with your application, and a clear copy of your current passport's identification page. The Iranian government "requests" that women observe Muslim dress codes in their passport photos.
Submit your visa application to the Iranian embassy or consulate at least several months before your planned trip. Also remember to submit the required application fee, which varies based upon which Iranian embassy or consulate processes your application.
