1- First of all, you should register in the BIO registration system (web site) in your specific profile; upload your photo and a copy of your passport .We should also know that in which Iranian embassy you plan to apply for visa. You have an option to choose the IKA airport for getting your visa on your arrival day. However this option is not available for the nationals of Afghanistan, Bangladesh, Colombia, Iraq, India, Pakistan, UK and USA.
2-We submit your information to the ministry of foreign affairs system in Tehran, get an authorization number and request for 15 days visa. If you plan to enter before July 15 and leave later July 22, please inform us via email email@example.com . This step usually takes 4 weeks on average.
3- You present your authorization number along with other required documents (completed visa application form, passport, two passports - size photos, travel insurance, visa fee and other documents depending on your nationality) to the embassy and get your visa. This usually takes one week.