You can enter Nepal through the air or one of the land borders.
1) By Air
Kathmandu, the capital of Nepal, has the only international airport in the country, Tribhuvan International Airport (TIA). TIA has 12 major international flight networks. Nepal Airlines Corporation (NAC) is the national flag carrier. It has direct flights to Delhi & Mumbai in India, Kuala Lumpur in Malaysia, Shanghai in China, Bangkok in Thailand, Dubai in the United Arab Emirates, Osaka in Japan, Hongkong, and Singapore.
Similarly, other international airlines connect Nepal with other cities in different countries. For instance, China Airlines offers direct flights from Kathmandu to Lhasa in the Tibetan Autonomous Region of China, Biman Bangladesh connects Dhaka in Bangladesh, Qatar Airways to Doha in Qatar, Thai International to Bangkok in Thailand, Druk Air to Paro in Bhutan, Gulf Air to Abu Dhabi in the United Arab Emirates, Indian Airlines to Delhi, Kolkata, and Varanasi in India.
Several flights connect Nepal with all European nations and the West as well.
2) By Road
Nepal has borders with India, China, and Tibet. To enter Nepal via land, the travellers must hold a valid passport and visa. The documents are used in the designated entry points (Nepal-India or Nepal-China border) for verification.