We have only one international airport and lots of border to entry point in Nepal. You can get arrival visa in airport. All Indian nationals do not need visa to enter Nepal but must have proof of identity. All other nationals need a visa to come Nepal, available from Nepalese Embassies or consulates or arrival at the border and at airport. A single entry visa cost is $ 40 and is valid for 30 days. You can renew your visa by paying $40 for extra one month. That you can pay for Nepali currency or dollar.
here is visa information link http://www.nepalimmigration.gov.np/content/visa-information.html